// SPDX-License-Identifier: (GPL-2.0 or BSD-3-Clause-Clear)
/**
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 */

/* ***************************************************************
*  Tuning parameters
*****************************************************************/
/*!
*  MAXWINDOWSIZE_DEFAULT :
*  maximum window size accepted by DStream, by default.
*  Frames requiring more memory will be rejected.
*/
#ifndef ZSTD_MAXWINDOWSIZE_DEFAULT
#define ZSTD_MAXWINDOWSIZE_DEFAULT ((1 << ZSTD_WINDOWLOG_MAX) + 1) /* defined within zstd.h */
#endif

/*-*******************************************************
*  Dependencies
*********************************************************/
#include "fse.h"
#include "huf.h"
#include "mem.h" /* low level memory routines */
#include "zstd_internal.h"
#include <malloc.h>
#include <linux/kernel.h>
#include <linux/compat.h>
#include <linux/string.h> /* memcpy, memmove, memset */

#define ZSTD_PREFETCH(ptr) __builtin_prefetch(ptr, 0, 0)

/*-*************************************
*  Macros
***************************************/
#define ZSTD_isError ERR_isError /* for inlining */
#define FSE_isError ERR_isError
#define HUF_isError ERR_isError

/*_*******************************************************
*  Memory operations
**********************************************************/
static void ZSTD_copy4(void *dst, const void *src) { memcpy(dst, src, 4); }

/*-*************************************************************
*   Context management
***************************************************************/
typedef enum {
        ZSTDds_getFrameHeaderSize,
        ZSTDds_decodeFrameHeader,
        ZSTDds_decodeBlockHeader,
        ZSTDds_decompressBlock,
        ZSTDds_decompressLastBlock,
        ZSTDds_checkChecksum,
        ZSTDds_decodeSkippableHeader,
        ZSTDds_skipFrame
} ZSTD_dStage;

typedef struct {
        FSE_DTable LLTable[FSE_DTABLE_SIZE_U32(LLFSELog)];
        FSE_DTable OFTable[FSE_DTABLE_SIZE_U32(OffFSELog)];
        FSE_DTable MLTable[FSE_DTABLE_SIZE_U32(MLFSELog)];
        HUF_DTable hufTable[HUF_DTABLE_SIZE(HufLog)]; /* can accommodate HUF_decompress4X */
        U64 workspace[HUF_DECOMPRESS_WORKSPACE_SIZE_U32 / 2];
        U32 rep[ZSTD_REP_NUM];
} ZSTD_entropyTables_t;

struct ZSTD_DCtx_s {
        const FSE_DTable *LLTptr;
        const FSE_DTable *MLTptr;
        const FSE_DTable *OFTptr;
        const HUF_DTable *HUFptr;
        ZSTD_entropyTables_t entropy;
        const void *previousDstEnd; /* detect continuity */
        const void *base;          /* start of curr segment */
        const void *vBase;        /* virtual start of previous segment if it was just before curr one */
        const void *dictEnd;    /* end of previous segment */
        size_t expected;
        ZSTD_frameParams fParams;
        blockType_e bType; /* used in ZSTD_decompressContinue(), to transfer blockType between header decoding and block decoding stages */
        ZSTD_dStage stage;
        U32 litEntropy;
        U32 fseEntropy;
        struct xxh64_state xxhState;
        size_t headerSize;
        U32 dictID;
        const BYTE *litPtr;
        ZSTD_customMem customMem;
        size_t litSize;
        size_t rleSize;
        BYTE litBuffer[ZSTD_BLOCKSIZE_ABSOLUTEMAX + WILDCOPY_OVERLENGTH];
        BYTE headerBuffer[ZSTD_FRAMEHEADERSIZE_MAX];
}; /* typedef'd to ZSTD_DCtx within "zstd.h" */

size_t ZSTD_DCtxWorkspaceBound(void) { return ZSTD_ALIGN(sizeof(ZSTD_stack)) + ZSTD_ALIGN(sizeof(ZSTD_DCtx)); }

size_t ZSTD_decompressBegin(ZSTD_DCtx *dctx)
{
        dctx->expected = ZSTD_frameHeaderSize_prefix;
        dctx->stage = ZSTDds_getFrameHeaderSize;
        dctx->previousDstEnd = NULL;
        dctx->base = NULL;
        dctx->vBase = NULL;
        dctx->dictEnd = NULL;
        dctx->entropy.hufTable[0] = (HUF_DTable)((HufLog)*0x1000001); /* cover both little and big endian */
        dctx->litEntropy = dctx->fseEntropy = 0;
        dctx->dictID = 0;
        ZSTD_STATIC_ASSERT(sizeof(dctx->entropy.rep) == sizeof(repStartValue));
        memcpy(dctx->entropy.rep, repStartValue, sizeof(repStartValue)); /* initial repcodes */
        dctx->LLTptr = dctx->entropy.LLTable;
        dctx->MLTptr = dctx->entropy.MLTable;
        dctx->OFTptr = dctx->entropy.OFTable;
        dctx->HUFptr = dctx->entropy.hufTable;
        return 0;
}

ZSTD_DCtx *ZSTD_createDCtx_advanced(ZSTD_customMem customMem)
{
        ZSTD_DCtx *dctx;

        if (!customMem.customAlloc || !customMem.customFree)
                return NULL;

        dctx = (ZSTD_DCtx *)ZSTD_malloc(sizeof(ZSTD_DCtx), customMem);
        if (!dctx)
                return NULL;
        memcpy(&dctx->customMem, &customMem, sizeof(customMem));
        ZSTD_decompressBegin(dctx);
        return dctx;
}

ZSTD_DCtx *ZSTD_initDCtx(void *workspace, size_t workspaceSize)
{
        ZSTD_customMem const stackMem = ZSTD_initStack(workspace, workspaceSize);
        return ZSTD_createDCtx_advanced(stackMem);
}

size_t ZSTD_freeDCtx(ZSTD_DCtx *dctx)
{
        if (dctx == NULL)
                return 0; /* support free on NULL */
        ZSTD_free(dctx, dctx->customMem);
        return 0; /* reserved as a potential error code in the future */
}

void ZSTD_copyDCtx(ZSTD_DCtx *dstDCtx, const ZSTD_DCtx *srcDCtx)
{
        size_t const workSpaceSize = (ZSTD_BLOCKSIZE_ABSOLUTEMAX + WILDCOPY_OVERLENGTH) + ZSTD_frameHeaderSize_max;
        memcpy(dstDCtx, srcDCtx, sizeof(ZSTD_DCtx) - workSpaceSize); /* no need to copy workspace */
}

static void ZSTD_refDDict(ZSTD_DCtx *dstDCtx, const ZSTD_DDict *ddict);

/*-*************************************************************
*   Decompression section
***************************************************************/

/*! ZSTD_isFrame() :
 *  Tells if the content of `buffer` starts with a valid Frame Identifier.
 *  Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
 *  Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
 *  Note 3 : Skippable Frame Identifiers are considered valid. */
unsigned ZSTD_isFrame(const void *buffer, size_t size)
{
        if (size < 4)
                return 0;
        {
                U32 const magic = ZSTD_readLE32(buffer);
                if (magic == ZSTD_MAGICNUMBER)
                        return 1;
                if ((magic & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START)
                        return 1;
        }
        return 0;
}

/** ZSTD_frameHeaderSize() :
*   srcSize must be >= ZSTD_frameHeaderSize_prefix.
*   @return : size of the Frame Header */
static size_t ZSTD_frameHeaderSize(const void *src, size_t srcSize)
{
        if (srcSize < ZSTD_frameHeaderSize_prefix)
                return ERROR(srcSize_wrong);
        {
                BYTE const fhd = ((const BYTE *)src)[4];
                U32 const dictID = fhd & 3;
                U32 const singleSegment = (fhd >> 5) & 1;
                U32 const fcsId = fhd >> 6;
                return ZSTD_frameHeaderSize_prefix + !singleSegment + ZSTD_did_fieldSize[dictID] + ZSTD_fcs_fieldSize[fcsId] + (singleSegment && !fcsId);
        }
}

/** ZSTD_getFrameParams() :
*   decode Frame Header, or require larger `srcSize`.
*   @return : 0, `fparamsPtr` is correctly filled,
*            >0, `srcSize` is too small, result is expected `srcSize`,
*             or an error code, which can be tested using ZSTD_isError() */
size_t ZSTD_getFrameParams(ZSTD_frameParams *fparamsPtr, const void *src, size_t srcSize)
{
        const BYTE *ip = (const BYTE *)src;

        if (srcSize < ZSTD_frameHeaderSize_prefix)
                return ZSTD_frameHeaderSize_prefix;
        if (ZSTD_readLE32(src) != ZSTD_MAGICNUMBER) {
                if ((ZSTD_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
                        if (srcSize < ZSTD_skippableHeaderSize)
                                return ZSTD_skippableHeaderSize; /* magic number + skippable frame length */
                        memset(fparamsPtr, 0, sizeof(*fparamsPtr));
                        fparamsPtr->frameContentSize = ZSTD_readLE32((const char *)src + 4);
                        fparamsPtr->windowSize = 0; /* windowSize==0 means a frame is skippable */
                        return 0;
                }
                return ERROR(prefix_unknown);
        }

        /* ensure there is enough `srcSize` to fully read/decode frame header */
        {
                size_t const fhsize = ZSTD_frameHeaderSize(src, srcSize);
                if (srcSize < fhsize)
                        return fhsize;
        }

        {
                BYTE const fhdByte = ip[4];
                size_t pos = 5;
                U32 const dictIDSizeCode = fhdByte & 3;
                U32 const checksumFlag = (fhdByte >> 2) & 1;
                U32 const singleSegment = (fhdByte >> 5) & 1;
                U32 const fcsID = fhdByte >> 6;
                U32 const windowSizeMax = 1U << ZSTD_WINDOWLOG_MAX;
                U32 windowSize = 0;
                U32 dictID = 0;
                U64 frameContentSize = 0;
                if ((fhdByte & 0x08) != 0)
                        return ERROR(frameParameter_unsupported); /* reserved bits, which must be zero */
                if (!singleSegment) {
                        BYTE const wlByte = ip[pos++];
                        U32 const windowLog = (wlByte >> 3) + ZSTD_WINDOWLOG_ABSOLUTEMIN;
                        if (windowLog > ZSTD_WINDOWLOG_MAX)
                                return ERROR(frameParameter_windowTooLarge); /* avoids issue with 1 << windowLog */
                        windowSize = (1U << windowLog);
                        windowSize += (windowSize >> 3) * (wlByte & 7);
                }

                switch (dictIDSizeCode) {
                default: /* impossible */
                case 0: break;
                case 1:
                        dictID = ip[pos];
                        pos++;
                        break;
                case 2:
                        dictID = ZSTD_readLE16(ip + pos);
                        pos += 2;
                        break;
                case 3:
                        dictID = ZSTD_readLE32(ip + pos);
                        pos += 4;
                        break;
                }
                switch (fcsID) {
                default: /* impossible */
                case 0:
                        if (singleSegment)
                                frameContentSize = ip[pos];
                        break;
                case 1: frameContentSize = ZSTD_readLE16(ip + pos) + 256; break;
                case 2: frameContentSize = ZSTD_readLE32(ip + pos); break;
                case 3: frameContentSize = ZSTD_readLE64(ip + pos); break;
                }
                if (!windowSize)
                        windowSize = (U32)frameContentSize;
                if (windowSize > windowSizeMax)
                        return ERROR(frameParameter_windowTooLarge);
                fparamsPtr->frameContentSize = frameContentSize;
                fparamsPtr->windowSize = windowSize;
                fparamsPtr->dictID = dictID;
                fparamsPtr->checksumFlag = checksumFlag;
        }
        return 0;
}

/** ZSTD_getFrameContentSize() :
*   compatible with legacy mode
*   @return : decompressed size of the single frame pointed to be `src` if known, otherwise
*             - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
*             - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) */
unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize)
{
        {
                ZSTD_frameParams fParams;
                if (ZSTD_getFrameParams(&fParams, src, srcSize) != 0)
                        return ZSTD_CONTENTSIZE_ERROR;
                if (fParams.windowSize == 0) {
                        /* Either skippable or empty frame, size == 0 either way */
                        return 0;
                } else if (fParams.frameContentSize != 0) {
                        return fParams.frameContentSize;
                } else {
                        return ZSTD_CONTENTSIZE_UNKNOWN;
                }
        }
}

/** ZSTD_findDecompressedSize() :
 *  compatible with legacy mode
 *  `srcSize` must be the exact length of some number of ZSTD compressed and/or
 *      skippable frames
 *  @return : decompressed size of the frames contained */
unsigned long long ZSTD_findDecompressedSize(const void *src, size_t srcSize)
{
        {
                unsigned long long totalDstSize = 0;
                while (srcSize >= ZSTD_frameHeaderSize_prefix) {
                        const U32 magicNumber = ZSTD_readLE32(src);

                        if ((magicNumber & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
                                size_t skippableSize;
                                if (srcSize < ZSTD_skippableHeaderSize)
                                        return ERROR(srcSize_wrong);
                                skippableSize = ZSTD_readLE32((const BYTE *)src + 4) + ZSTD_skippableHeaderSize;
                                if (srcSize < skippableSize) {
                                        return ZSTD_CONTENTSIZE_ERROR;
                                }

                                src = (const BYTE *)src + skippableSize;
                                srcSize -= skippableSize;
                                continue;
                        }

                        {
                                unsigned long long const ret = ZSTD_getFrameContentSize(src, srcSize);
                                if (ret >= ZSTD_CONTENTSIZE_ERROR)
                                        return ret;

                                /* check for overflow */
                                if (totalDstSize + ret < totalDstSize)
                                        return ZSTD_CONTENTSIZE_ERROR;
                                totalDstSize += ret;
                        }
                        {
                                size_t const frameSrcSize = ZSTD_findFrameCompressedSize(src, srcSize);
                                if (ZSTD_isError(frameSrcSize)) {
                                        return ZSTD_CONTENTSIZE_ERROR;
                                }

                                src = (const BYTE *)src + frameSrcSize;
                                srcSize -= frameSrcSize;
                        }
                }

                if (srcSize) {
                        return ZSTD_CONTENTSIZE_ERROR;
                }

                return totalDstSize;
        }
}

/** ZSTD_decodeFrameHeader() :
*   `headerSize` must be the size provided by ZSTD_frameHeaderSize().
*   @return : 0 if success, or an error code, which can be tested using ZSTD_isError() */
static size_t ZSTD_decodeFrameHeader(ZSTD_DCtx *dctx, const void *src, size_t headerSize)
{
        size_t const result = ZSTD_getFrameParams(&(dctx->fParams), src, headerSize);
        if (ZSTD_isError(result))
                return result; /* invalid header */
        if (result > 0)
                return ERROR(srcSize_wrong); /* headerSize too small */
        if (dctx->fParams.dictID && (dctx->dictID != dctx->fParams.dictID))
                return ERROR(dictionary_wrong);
        if (dctx->fParams.checksumFlag)
                xxh64_reset(&dctx->xxhState, 0);
        return 0;
}

typedef struct {
        blockType_e blockType;
        U32 lastBlock;
        U32 origSize;
} blockProperties_t;

/*! ZSTD_getcBlockSize() :
*   Provides the size of compressed block from block header `src` */
size_t ZSTD_getcBlockSize(const void *src, size_t srcSize, blockProperties_t *bpPtr)
{
        if (srcSize < ZSTD_blockHeaderSize)
                return ERROR(srcSize_wrong);
        {
                U32 const cBlockHeader = ZSTD_readLE24(src);
                U32 const cSize = cBlockHeader >> 3;
                bpPtr->lastBlock = cBlockHeader & 1;
                bpPtr->blockType = (blockType_e)((cBlockHeader >> 1) & 3);
                bpPtr->origSize = cSize; /* only useful for RLE */
                if (bpPtr->blockType == bt_rle)
                        return 1;
                if (bpPtr->blockType == bt_reserved)
                        return ERROR(corruption_detected);
                return cSize;
        }
}

static size_t ZSTD_copyRawBlock(void *dst, size_t dstCapacity, const void *src, size_t srcSize)
{
        if (srcSize > dstCapacity)
                return ERROR(dstSize_tooSmall);
        memcpy(dst, src, srcSize);
        return srcSize;
}

static size_t ZSTD_setRleBlock(void *dst, size_t dstCapacity, const void *src, size_t srcSize, size_t regenSize)
{
        if (srcSize != 1)
                return ERROR(srcSize_wrong);
        if (regenSize > dstCapacity)
                return ERROR(dstSize_tooSmall);
        memset(dst, *(const BYTE *)src, regenSize);
        return regenSize;
}

/*! ZSTD_decodeLiteralsBlock() :
        @return : nb of bytes read from src (< srcSize ) */
size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx *dctx, const void *src, size_t srcSize) /* note : srcSize < BLOCKSIZE */
{
        if (srcSize < MIN_CBLOCK_SIZE)
                return ERROR(corruption_detected);

        {
                const BYTE *const istart = (const BYTE *)src;
                symbolEncodingType_e const litEncType = (symbolEncodingType_e)(istart[0] & 3);

                switch (litEncType) {
                case set_repeat:
                        if (dctx->litEntropy == 0)
                                return ERROR(dictionary_corrupted);
                /* fall-through */
                case set_compressed:
                        if (srcSize < 5)
                                return ERROR(corruption_detected); /* srcSize >= MIN_CBLOCK_SIZE == 3; here we need up to 5 for case 3 */
                        {
                                size_t lhSize, litSize, litCSize;
                                U32 singleStream = 0;
                                U32 const lhlCode = (istart[0] >> 2) & 3;
                                U32 const lhc = ZSTD_readLE32(istart);
                                switch (lhlCode) {
                                case 0:
                                case 1:
                                default: /* note : default is impossible, since lhlCode into [0..3] */
                                        /* 2 - 2 - 10 - 10 */
                                        singleStream = !lhlCode;
                                        lhSize = 3;
                                        litSize = (lhc >> 4) & 0x3FF;
                                        litCSize = (lhc >> 14) & 0x3FF;
                                        break;
                                case 2:
                                        /* 2 - 2 - 14 - 14 */
                                        lhSize = 4;
                                        litSize = (lhc >> 4) & 0x3FFF;
                                        litCSize = lhc >> 18;
                                        break;
                                case 3:
                                        /* 2 - 2 - 18 - 18 */
                                        lhSize = 5;
                                        litSize = (lhc >> 4) & 0x3FFFF;
                                        litCSize = (lhc >> 22) + (istart[4] << 10);
                                        break;
                                }
                                if (litSize > ZSTD_BLOCKSIZE_ABSOLUTEMAX)
                                        return ERROR(corruption_detected);
                                if (litCSize + lhSize > srcSize)
                                        return ERROR(corruption_detected);

                                if (HUF_isError(
                                        (litEncType == set_repeat)
                                            ? (singleStream ? HUF_decompress1X_usingDTable(dctx->litBuffer, litSize, istart + lhSize, litCSize, dctx->HUFptr)
                                                            : HUF_decompress4X_usingDTable(dctx->litBuffer, litSize, istart + lhSize, litCSize, dctx->HUFptr))
                                            : (singleStream
                                                   ? HUF_decompress1X2_DCtx_wksp(dctx->entropy.hufTable, dctx->litBuffer, litSize, istart + lhSize, litCSize,
                                                                                 dctx->entropy.workspace, sizeof(dctx->entropy.workspace))
                                                   : HUF_decompress4X_hufOnly_wksp(dctx->entropy.hufTable, dctx->litBuffer, litSize, istart + lhSize, litCSize,
                                                                                   dctx->entropy.workspace, sizeof(dctx->entropy.workspace)))))
                                        return ERROR(corruption_detected);

                                dctx->litPtr = dctx->litBuffer;
                                dctx->litSize = litSize;
                                dctx->litEntropy = 1;
                                if (litEncType == set_compressed)
                                        dctx->HUFptr = dctx->entropy.hufTable;
                                memset(dctx->litBuffer + dctx->litSize, 0, WILDCOPY_OVERLENGTH);
                                return litCSize + lhSize;
                        }

                case set_basic: {
                        size_t litSize, lhSize;
                        U32 const lhlCode = ((istart[0]) >> 2) & 3;
                        switch (lhlCode) {
                        case 0:
                        case 2:
                        default: /* note : default is impossible, since lhlCode into [0..3] */
                                lhSize = 1;
                                litSize = istart[0] >> 3;
                                break;
                        case 1:
                                lhSize = 2;
                                litSize = ZSTD_readLE16(istart) >> 4;
                                break;
                        case 3:
                                lhSize = 3;
                                litSize = ZSTD_readLE24(istart) >> 4;
                                break;
                        }

                        if (lhSize + litSize + WILDCOPY_OVERLENGTH > srcSize) { /* risk reading beyond src buffer with wildcopy */
                                if (litSize + lhSize > srcSize)
                                        return ERROR(corruption_detected);
                                memcpy(dctx->litBuffer, istart + lhSize, litSize);
                                dctx->litPtr = dctx->litBuffer;
                                dctx->litSize = litSize;
                                memset(dctx->litBuffer + dctx->litSize, 0, WILDCOPY_OVERLENGTH);
                                return lhSize + litSize;
                        }
                        /* direct reference into compressed stream */
                        dctx->litPtr = istart + lhSize;
                        dctx->litSize = litSize;
                        return lhSize + litSize;
                }

                case set_rle: {
                        U32 const lhlCode = ((istart[0]) >> 2) & 3;
                        size_t litSize, lhSize;
                        switch (lhlCode) {
                        case 0:
                        case 2:
                        default: /* note : default is impossible, since lhlCode into [0..3] */
                                lhSize = 1;
                                litSize = istart[0] >> 3;
                                break;
                        case 1:
                                lhSize = 2;
                                litSize = ZSTD_readLE16(istart) >> 4;
                                break;
                        case 3:
                                lhSize = 3;
                                litSize = ZSTD_readLE24(istart) >> 4;
                                if (srcSize < 4)
                                        return ERROR(corruption_detected); /* srcSize >= MIN_CBLOCK_SIZE == 3; here we need lhSize+1 = 4 */
                                break;
                        }
                        if (litSize > ZSTD_BLOCKSIZE_ABSOLUTEMAX)
                                return ERROR(corruption_detected);
                        memset(dctx->litBuffer, istart[lhSize], litSize + WILDCOPY_OVERLENGTH);
                        dctx->litPtr = dctx->litBuffer;
                        dctx->litSize = litSize;
                        return lhSize + 1;
                }
                default:
                        return ERROR(corruption_detected); /* impossible */
                }
        }
}

typedef union {
        FSE_decode_t realData;
        U32 alignedBy4;
} FSE_decode_t4;

static const FSE_decode_t4 LL_defaultDTable[(1 << LL_DEFAULTNORMLOG) + 1] = {
    {{LL_DEFAULTNORMLOG, 1, 1}}, /* header : tableLog, fastMode, fastMode */
    {{0, 0, 4}},                 /* 0 : base, symbol, bits */
    {{16, 0, 4}},
    {{32, 1, 5}},
    {{0, 3, 5}},
    {{0, 4, 5}},
    {{0, 6, 5}},
    {{0, 7, 5}},
    {{0, 9, 5}},
    {{0, 10, 5}},
    {{0, 12, 5}},
    {{0, 14, 6}},
    {{0, 16, 5}},
    {{0, 18, 5}},
    {{0, 19, 5}},
    {{0, 21, 5}},
    {{0, 22, 5}},
    {{0, 24, 5}},
    {{32, 25, 5}},
    {{0, 26, 5}},
    {{0, 27, 6}},
    {{0, 29, 6}},
    {{0, 31, 6}},
    {{32, 0, 4}},
    {{0, 1, 4}},
    {{0, 2, 5}},
    {{32, 4, 5}},
    {{0, 5, 5}},
    {{32, 7, 5}},
    {{0, 8, 5}},
    {{32, 10, 5}},
    {{0, 11, 5}},
    {{0, 13, 6}},
    {{32, 16, 5}},
    {{0, 17, 5}},
    {{32, 19, 5}},
    {{0, 20, 5}},
    {{32, 22, 5}},
    {{0, 23, 5}},
    {{0, 25, 4}},
    {{16, 25, 4}},
    {{32, 26, 5}},
    {{0, 28, 6}},
    {{0, 30, 6}},
    {{48, 0, 4}},
    {{16, 1, 4}},
    {{32, 2, 5}},
    {{32, 3, 5}},
    {{32, 5, 5}},
    {{32, 6, 5}},
    {{32, 8, 5}},
    {{32, 9, 5}},
    {{32, 11, 5}},
    {{32, 12, 5}},
    {{0, 15, 6}},
    {{32, 17, 5}},
    {{32, 18, 5}},
    {{32, 20, 5}},
    {{32, 21, 5}},
    {{32, 23, 5}},
    {{32, 24, 5}},
    {{0, 35, 6}},
    {{0, 34, 6}},
    {{0, 33, 6}},
    {{0, 32, 6}},
}; /* LL_defaultDTable */

static const FSE_decode_t4 ML_defaultDTable[(1 << ML_DEFAULTNORMLOG) + 1] = {
    {{ML_DEFAULTNORMLOG, 1, 1}}, /* header : tableLog, fastMode, fastMode */
    {{0, 0, 6}},                 /* 0 : base, symbol, bits */
    {{0, 1, 4}},
    {{32, 2, 5}},
    {{0, 3, 5}},
    {{0, 5, 5}},
    {{0, 6, 5}},
    {{0, 8, 5}},
    {{0, 10, 6}},
    {{0, 13, 6}},
    {{0, 16, 6}},
    {{0, 19, 6}},
    {{0, 22, 6}},
    {{0, 25, 6}},
    {{0, 28, 6}},
    {{0, 31, 6}},
    {{0, 33, 6}},
    {{0, 35, 6}},
    {{0, 37, 6}},
    {{0, 39, 6}},
    {{0, 41, 6}},
    {{0, 43, 6}},
    {{0, 45, 6}},
    {{16, 1, 4}},
    {{0, 2, 4}},
    {{32, 3, 5}},
    {{0, 4, 5}},
    {{32, 6, 5}},
    {{0, 7, 5}},
    {{0, 9, 6}},
    {{0, 12, 6}},
    {{0, 15, 6}},
    {{0, 18, 6}},
    {{0, 21, 6}},
    {{0, 24, 6}},
    {{0, 27, 6}},
    {{0, 30, 6}},
    {{0, 32, 6}},
    {{0, 34, 6}},
    {{0, 36, 6}},
    {{0, 38, 6}},
    {{0, 40, 6}},
    {{0, 42, 6}},
    {{0, 44, 6}},
    {{32, 1, 4}},
    {{48, 1, 4}},
    {{16, 2, 4}},
    {{32, 4, 5}},
    {{32, 5, 5}},
    {{32, 7, 5}},
    {{32, 8, 5}},
    {{0, 11, 6}},
    {{0, 14, 6}},
    {{0, 17, 6}},
    {{0, 20, 6}},
    {{0, 23, 6}},
    {{0, 26, 6}},
    {{0, 29, 6}},
    {{0, 52, 6}},
    {{0, 51, 6}},
    {{0, 50, 6}},
    {{0, 49, 6}},
    {{0, 48, 6}},
    {{0, 47, 6}},
    {{0, 46, 6}},
}; /* ML_defaultDTable */

static const FSE_decode_t4 OF_defaultDTable[(1 << OF_DEFAULTNORMLOG) + 1] = {
    {{OF_DEFAULTNORMLOG, 1, 1}}, /* header : tableLog, fastMode, fastMode */
    {{0, 0, 5}},                 /* 0 : base, symbol, bits */
    {{0, 6, 4}},
    {{0, 9, 5}},
    {{0, 15, 5}},
    {{0, 21, 5}},
    {{0, 3, 5}},
    {{0, 7, 4}},
    {{0, 12, 5}},
    {{0, 18, 5}},
    {{0, 23, 5}},
    {{0, 5, 5}},
    {{0, 8, 4}},
    {{0, 14, 5}},
    {{0, 20, 5}},
    {{0, 2, 5}},
    {{16, 7, 4}},
    {{0, 11, 5}},
    {{0, 17, 5}},
    {{0, 22, 5}},
    {{0, 4, 5}},
    {{16, 8, 4}},
    {{0, 13, 5}},
    {{0, 19, 5}},
    {{0, 1, 5}},
    {{16, 6, 4}},
    {{0, 10, 5}},
    {{0, 16, 5}},
    {{0, 28, 5}},
    {{0, 27, 5}},
    {{0, 26, 5}},
    {{0, 25, 5}},
    {{0, 24, 5}},
}; /* OF_defaultDTable */

/*! ZSTD_buildSeqTable() :
        @return : nb bytes read from src,
                          or an error code if it fails, testable with ZSTD_isError()
*/
static size_t ZSTD_buildSeqTable(FSE_DTable *DTableSpace, const FSE_DTable **DTablePtr, symbolEncodingType_e type, U32 max, U32 maxLog, const void *src,
                                 size_t srcSize, const FSE_decode_t4 *defaultTable, U32 flagRepeatTable, void *workspace, size_t workspaceSize)
{
        const void *const tmpPtr = defaultTable; /* bypass strict aliasing */
        switch (type) {
        case set_rle:
                if (!srcSize)
                        return ERROR(srcSize_wrong);
                if ((*(const BYTE *)src) > max)
                        return ERROR(corruption_detected);
                FSE_buildDTable_rle(DTableSpace, *(const BYTE *)src);
                *DTablePtr = DTableSpace;
                return 1;
        case set_basic: *DTablePtr = (const FSE_DTable *)tmpPtr; return 0;
        case set_repeat:
                if (!flagRepeatTable)
                        return ERROR(corruption_detected);
                return 0;
        default: /* impossible */
        case set_compressed: {
                U32 tableLog;
                S16 *norm = (S16 *)workspace;
                size_t const spaceUsed32 = ALIGN(sizeof(S16) * (MaxSeq + 1), sizeof(U32)) >> 2;

                if ((spaceUsed32 << 2) > workspaceSize)
                        return ERROR(GENERIC);
                workspace = (U32 *)workspace + spaceUsed32;
                workspaceSize -= (spaceUsed32 << 2);
                {
                        size_t const headerSize = FSE_readNCount(norm, &max, &tableLog, src, srcSize);
                        if (FSE_isError(headerSize))
                                return ERROR(corruption_detected);
                        if (tableLog > maxLog)
                                return ERROR(corruption_detected);
                        FSE_buildDTable_wksp(DTableSpace, norm, max, tableLog, workspace, workspaceSize);
                        *DTablePtr = DTableSpace;
                        return headerSize;
                }
        }
        }
}

size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx *dctx, int *nbSeqPtr, const void *src, size_t srcSize)
{
        const BYTE *const istart = (const BYTE *const)src;
        const BYTE *const iend = istart + srcSize;
        const BYTE *ip = istart;

        /* check */
        if (srcSize < MIN_SEQUENCES_SIZE)
                return ERROR(srcSize_wrong);

        /* SeqHead */
        {
                int nbSeq = *ip++;
                if (!nbSeq) {
                        *nbSeqPtr = 0;
                        return 1;
                }
                if (nbSeq > 0x7F) {
                        if (nbSeq == 0xFF) {
                                if (ip + 2 > iend)
                                        return ERROR(srcSize_wrong);
                                nbSeq = ZSTD_readLE16(ip) + LONGNBSEQ, ip += 2;
                        } else {
                                if (ip >= iend)
                                        return ERROR(srcSize_wrong);
                                nbSeq = ((nbSeq - 0x80) << 8) + *ip++;
                        }
                }
                *nbSeqPtr = nbSeq;
        }

        /* FSE table descriptors */
        if (ip + 4 > iend)
                return ERROR(srcSize_wrong); /* minimum possible size */
        {
                symbolEncodingType_e const LLtype = (symbolEncodingType_e)(*ip >> 6);
                symbolEncodingType_e const OFtype = (symbolEncodingType_e)((*ip >> 4) & 3);
                symbolEncodingType_e const MLtype = (symbolEncodingType_e)((*ip >> 2) & 3);
                ip++;

                /* Build DTables */
                {
                        size_t const llhSize = ZSTD_buildSeqTable(dctx->entropy.LLTable, &dctx->LLTptr, LLtype, MaxLL, LLFSELog, ip, iend - ip,
                                                                  LL_defaultDTable, dctx->fseEntropy, dctx->entropy.workspace, sizeof(dctx->entropy.workspace));
                        if (ZSTD_isError(llhSize))
                                return ERROR(corruption_detected);
                        ip += llhSize;
                }
                {
                        size_t const ofhSize = ZSTD_buildSeqTable(dctx->entropy.OFTable, &dctx->OFTptr, OFtype, MaxOff, OffFSELog, ip, iend - ip,
                                                                  OF_defaultDTable, dctx->fseEntropy, dctx->entropy.workspace, sizeof(dctx->entropy.workspace));
                        if (ZSTD_isError(ofhSize))
                                return ERROR(corruption_detected);
                        ip += ofhSize;
                }
                {
                        size_t const mlhSize = ZSTD_buildSeqTable(dctx->entropy.MLTable, &dctx->MLTptr, MLtype, MaxML, MLFSELog, ip, iend - ip,
                                                                  ML_defaultDTable, dctx->fseEntropy, dctx->entropy.workspace, sizeof(dctx->entropy.workspace));
                        if (ZSTD_isError(mlhSize))
                                return ERROR(corruption_detected);
                        ip += mlhSize;
                }
        }

        return ip - istart;
}

typedef struct {
        size_t litLength;
        size_t matchLength;
        size_t offset;
        const BYTE *match;
} seq_t;

typedef struct {
        BIT_DStream_t DStream;
        FSE_DState_t stateLL;
        FSE_DState_t stateOffb;
        FSE_DState_t stateML;
        size_t prevOffset[ZSTD_REP_NUM];
        const BYTE *base;
        size_t pos;
        uPtrDiff gotoDict;
} seqState_t;

FORCE_NOINLINE
size_t ZSTD_execSequenceLast7(BYTE *op, BYTE *const oend, seq_t sequence, const BYTE **litPtr, const BYTE *const litLimit, const BYTE *const base,
                              const BYTE *const vBase, const BYTE *const dictEnd)
{
        BYTE *const oLitEnd = op + sequence.litLength;
        size_t const sequenceLength = sequence.litLength + sequence.matchLength;
        BYTE *const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
        BYTE *const oend_w = oend - WILDCOPY_OVERLENGTH;
        const BYTE *const iLitEnd = *litPtr + sequence.litLength;
        const BYTE *match = oLitEnd - sequence.offset;

        /* check */
        if (oMatchEnd > oend)
                return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend */
        if (iLitEnd > litLimit)
                return ERROR(corruption_detected); /* over-read beyond lit buffer */
        if (oLitEnd <= oend_w)
                return ERROR(GENERIC); /* Precondition */

        /* copy literals */
        if (op < oend_w) {
                ZSTD_wildcopy(op, *litPtr, oend_w - op);
                *litPtr += oend_w - op;
                op = oend_w;
        }
        while (op < oLitEnd)
                *op++ = *(*litPtr)++;

        /* copy Match */
        if (sequence.offset > (size_t)(oLitEnd - base)) {
                /* offset beyond prefix */
                if (sequence.offset > (size_t)(oLitEnd - vBase))
                        return ERROR(corruption_detected);
                match = dictEnd - (base - match);
                if (match + sequence.matchLength <= dictEnd) {
                        memmove(oLitEnd, match, sequence.matchLength);
                        return sequenceLength;
                }
                /* span extDict & currPrefixSegment */
                {
                        size_t const length1 = dictEnd - match;
                        memmove(oLitEnd, match, length1);
                        op = oLitEnd + length1;
                        sequence.matchLength -= length1;
                        match = base;
                }
        }
        while (op < oMatchEnd)
                *op++ = *match++;
        return sequenceLength;
}

static seq_t ZSTD_decodeSequence(seqState_t *seqState)
{
        seq_t seq;

        U32 const llCode = FSE_peekSymbol(&seqState->stateLL);
        U32 const mlCode = FSE_peekSymbol(&seqState->stateML);
        U32 const ofCode = FSE_peekSymbol(&seqState->stateOffb); /* <= maxOff, by table construction */

        U32 const llBits = LL_bits[llCode];
        U32 const mlBits = ML_bits[mlCode];
        U32 const ofBits = ofCode;
        U32 const totalBits = llBits + mlBits + ofBits;

        static const U32 LL_base[MaxLL + 1] = {0,  1,  2,  3,  4,  5,  6,  7,  8,    9,     10,    11,    12,    13,     14,     15,     16,     18,
                                               20, 22, 24, 28, 32, 40, 48, 64, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000, 0x8000, 0x10000};

        static const U32 ML_base[MaxML + 1] = {3,  4,  5,  6,  7,  8,  9,  10,   11,    12,    13,    14,    15,     16,     17,     18,     19,     20,
                                               21, 22, 23, 24, 25, 26, 27, 28,   29,    30,    31,    32,    33,     34,     35,     37,     39,     41,
                                               43, 47, 51, 59, 67, 83, 99, 0x83, 0x103, 0x203, 0x403, 0x803, 0x1003, 0x2003, 0x4003, 0x8003, 0x10003};

        static const U32 OF_base[MaxOff + 1] = {0,       1,     1,      5,      0xD,      0x1D,      0x3D,      0x7D,      0xFD,     0x1FD,
                                                0x3FD,   0x7FD,    0xFFD,    0x1FFD,   0x3FFD,   0x7FFD,    0xFFFD,    0x1FFFD,   0x3FFFD,  0x7FFFD,
                                                0xFFFFD, 0x1FFFFD, 0x3FFFFD, 0x7FFFFD, 0xFFFFFD, 0x1FFFFFD, 0x3FFFFFD, 0x7FFFFFD, 0xFFFFFFD};

        /* sequence */
        {
                size_t offset;
                if (!ofCode)
                        offset = 0;
                else {
                        offset = OF_base[ofCode] + BIT_readBitsFast(&seqState->DStream, ofBits); /* <=  (ZSTD_WINDOWLOG_MAX-1) bits */
                        if (ZSTD_32bits())
                                BIT_reloadDStream(&seqState->DStream);
                }

                if (ofCode <= 1) {
                        offset += (llCode == 0);
                        if (offset) {
                                size_t temp = (offset == 3) ? seqState->prevOffset[0] - 1 : seqState->prevOffset[offset];
                                temp += !temp; /* 0 is not valid; input is corrupted; force offset to 1 */
                                if (offset != 1)
                                        seqState->prevOffset[2] = seqState->prevOffset[1];
                                seqState->prevOffset[1] = seqState->prevOffset[0];
                                seqState->prevOffset[0] = offset = temp;
                        } else {
                                offset = seqState->prevOffset[0];
                        }
                } else {
                        seqState->prevOffset[2] = seqState->prevOffset[1];
                        seqState->prevOffset[1] = seqState->prevOffset[0];
                        seqState->prevOffset[0] = offset;
                }
                seq.offset = offset;
        }

        seq.matchLength = ML_base[mlCode] + ((mlCode > 31) ? BIT_readBitsFast(&seqState->DStream, mlBits) : 0); /* <=  16 bits */
        if (ZSTD_32bits() && (mlBits + llBits > 24))
                BIT_reloadDStream(&seqState->DStream);

        seq.litLength = LL_base[llCode] + ((llCode > 15) ? BIT_readBitsFast(&seqState->DStream, llBits) : 0); /* <=  16 bits */
        if (ZSTD_32bits() || (totalBits > 64 - 7 - (LLFSELog + MLFSELog + OffFSELog)))
                BIT_reloadDStream(&seqState->DStream);

        /* ANS state update */
        FSE_updateState(&seqState->stateLL, &seqState->DStream); /* <=  9 bits */
        FSE_updateState(&seqState->stateML, &seqState->DStream); /* <=  9 bits */
        if (ZSTD_32bits())
                BIT_reloadDStream(&seqState->DStream);             /* <= 18 bits */
        FSE_updateState(&seqState->stateOffb, &seqState->DStream); /* <=  8 bits */

        seq.match = NULL;

        return seq;
}

FORCE_INLINE
size_t ZSTD_execSequence(BYTE *op, BYTE *const oend, seq_t sequence, const BYTE **litPtr, const BYTE *const litLimit, const BYTE *const base,
                         const BYTE *const vBase, const BYTE *const dictEnd)
{

        BYTE *const oLitEnd = op + sequence.litLength;
        size_t const sequenceLength = sequence.litLength + sequence.matchLength;
        BYTE *const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
        BYTE *const oend_w = oend - WILDCOPY_OVERLENGTH;
        const BYTE *const iLitEnd = *litPtr + sequence.litLength;
        const BYTE *match = oLitEnd - sequence.offset;

        /* check */
        if (oMatchEnd > oend)
                return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend */
        if (iLitEnd > litLimit)
                return ERROR(corruption_detected); /* over-read beyond lit buffer */
        if (oLitEnd > oend_w)
                return ZSTD_execSequenceLast7(op, oend, sequence, litPtr, litLimit, base, vBase, dictEnd);

        /* copy Literals */
        ZSTD_copy8(op, *litPtr);
        if (sequence.litLength > 8)
                ZSTD_wildcopy(op + 8, (*litPtr) + 8,
                              sequence.litLength - 8); /* note : since oLitEnd <= oend-WILDCOPY_OVERLENGTH, no risk of overwrite beyond oend */
        op = oLitEnd;
        *litPtr = iLitEnd; /* update for next sequence */

        /* copy Match */
        if (sequence.offset > (size_t)(oLitEnd - base)) {
                /* offset beyond prefix */
                if (sequence.offset > (size_t)(oLitEnd - vBase))
                        return ERROR(corruption_detected);
                match = dictEnd + (match - base);
                if (match + sequence.matchLength <= dictEnd) {
                        memmove(oLitEnd, match, sequence.matchLength);
                        return sequenceLength;
                }
                /* span extDict & currPrefixSegment */
                {
                        size_t const length1 = dictEnd - match;
                        memmove(oLitEnd, match, length1);
                        op = oLitEnd + length1;
                        sequence.matchLength -= length1;
                        match = base;
                        if (op > oend_w || sequence.matchLength < MINMATCH) {
                                U32 i;
                                for (i = 0; i < sequence.matchLength; ++i)
                                        op[i] = match[i];
                                return sequenceLength;
                        }
                }
        }
        /* Requirement: op <= oend_w && sequence.matchLength >= MINMATCH */

        /* match within prefix */
        if (sequence.offset < 8) {
                /* close range match, overlap */
                static const U32 dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4};   /* added */
                static const int dec64table[] = {8, 8, 8, 7, 8, 9, 10, 11}; /* subtracted */
                int const sub2 = dec64table[sequence.offset];
                op[0] = match[0];
                op[1] = match[1];
                op[2] = match[2];
                op[3] = match[3];
                match += dec32table[sequence.offset];
                ZSTD_copy4(op + 4, match);
                match -= sub2;
        } else {
                ZSTD_copy8(op, match);
        }
        op += 8;
        match += 8;

        if (oMatchEnd > oend - (16 - MINMATCH)) {
                if (op < oend_w) {
                        ZSTD_wildcopy(op, match, oend_w - op);
                        match += oend_w - op;
                        op = oend_w;
                }
                while (op < oMatchEnd)
                        *op++ = *match++;
        } else {
                ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength - 8); /* works even if matchLength < 8 */
        }
        return sequenceLength;
}

static size_t ZSTD_decompressSequences(ZSTD_DCtx *dctx, void *dst, size_t maxDstSize, const void *seqStart, size_t seqSize)
{
        const BYTE *ip = (const BYTE *)seqStart;
        const BYTE *const iend = ip + seqSize;
        BYTE *const ostart = (BYTE * const)dst;
        BYTE *const oend = ostart + maxDstSize;
        BYTE *op = ostart;
        const BYTE *litPtr = dctx->litPtr;
        const BYTE *const litEnd = litPtr + dctx->litSize;
        const BYTE *const base = (const BYTE *)(dctx->base);
        const BYTE *const vBase = (const BYTE *)(dctx->vBase);
        const BYTE *const dictEnd = (const BYTE *)(dctx->dictEnd);
        int nbSeq;

        /* Build Decoding Tables */
        {
                size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, seqSize);
                if (ZSTD_isError(seqHSize))
                        return seqHSize;
                ip += seqHSize;
        }

        /* Regen sequences */
        if (nbSeq) {
                seqState_t seqState;
                dctx->fseEntropy = 1;
                {
                        U32 i;
                        for (i = 0; i < ZSTD_REP_NUM; i++)
                                seqState.prevOffset[i] = dctx->entropy.rep[i];
                }
                CHECK_E(BIT_initDStream(&seqState.DStream, ip, iend - ip), corruption_detected);
                FSE_initDState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr);
                FSE_initDState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr);
                FSE_initDState(&seqState.stateML, &seqState.DStream, dctx->MLTptr);

                for (; (BIT_reloadDStream(&(seqState.DStream)) <= BIT_DStream_completed) && nbSeq;) {
                        nbSeq--;
                        {
                                seq_t const sequence = ZSTD_decodeSequence(&seqState);
                                size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litEnd, base, vBase, dictEnd);
                                if (ZSTD_isError(oneSeqSize))
                                        return oneSeqSize;
                                op += oneSeqSize;
                        }
                }

                /* check if reached exact end */
                if (nbSeq)
                        return ERROR(corruption_detected);
                /* save reps for next block */
                {
                        U32 i;
                        for (i = 0; i < ZSTD_REP_NUM; i++)
                                dctx->entropy.rep[i] = (U32)(seqState.prevOffset[i]);
                }
        }

        /* last literal segment */
        {
                size_t const lastLLSize = litEnd - litPtr;
                if (lastLLSize > (size_t)(oend - op))
                        return ERROR(dstSize_tooSmall);
                memcpy(op, litPtr, lastLLSize);
                op += lastLLSize;
        }

        return op - ostart;
}

FORCE_INLINE seq_t ZSTD_decodeSequenceLong_generic(seqState_t *seqState, int const longOffsets)
{
        seq_t seq;

        U32 const llCode = FSE_peekSymbol(&seqState->stateLL);
        U32 const mlCode = FSE_peekSymbol(&seqState->stateML);
        U32 const ofCode = FSE_peekSymbol(&seqState->stateOffb); /* <= maxOff, by table construction */

        U32 const llBits = LL_bits[llCode];
        U32 const mlBits = ML_bits[mlCode];
        U32 const ofBits = ofCode;
        U32 const totalBits = llBits + mlBits + ofBits;

        static const U32 LL_base[MaxLL + 1] = {0,  1,  2,  3,  4,  5,  6,  7,  8,    9,     10,    11,    12,    13,     14,     15,     16,     18,
                                               20, 22, 24, 28, 32, 40, 48, 64, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000, 0x8000, 0x10000};

        static const U32 ML_base[MaxML + 1] = {3,  4,  5,  6,  7,  8,  9,  10,   11,    12,    13,    14,    15,     16,     17,     18,     19,     20,
                                               21, 22, 23, 24, 25, 26, 27, 28,   29,    30,    31,    32,    33,     34,     35,     37,     39,     41,
                                               43, 47, 51, 59, 67, 83, 99, 0x83, 0x103, 0x203, 0x403, 0x803, 0x1003, 0x2003, 0x4003, 0x8003, 0x10003};

        static const U32 OF_base[MaxOff + 1] = {0,       1,     1,      5,      0xD,      0x1D,      0x3D,      0x7D,      0xFD,     0x1FD,
                                                0x3FD,   0x7FD,    0xFFD,    0x1FFD,   0x3FFD,   0x7FFD,    0xFFFD,    0x1FFFD,   0x3FFFD,  0x7FFFD,
                                                0xFFFFD, 0x1FFFFD, 0x3FFFFD, 0x7FFFFD, 0xFFFFFD, 0x1FFFFFD, 0x3FFFFFD, 0x7FFFFFD, 0xFFFFFFD};

        /* sequence */
        {
                size_t offset;
                if (!ofCode)
                        offset = 0;
                else {
                        if (longOffsets) {
                                int const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN);
                                offset = OF_base[ofCode] + (BIT_readBitsFast(&seqState->DStream, ofBits - extraBits) << extraBits);
                                if (ZSTD_32bits() || extraBits)
                                        BIT_reloadDStream(&seqState->DStream);
                                if (extraBits)
                                        offset += BIT_readBitsFast(&seqState->DStream, extraBits);
                        } else {
                                offset = OF_base[ofCode] + BIT_readBitsFast(&seqState->DStream, ofBits); /* <=  (ZSTD_WINDOWLOG_MAX-1) bits */
                                if (ZSTD_32bits())
                                        BIT_reloadDStream(&seqState->DStream);
                        }
                }

                if (ofCode <= 1) {
                        offset += (llCode == 0);
                        if (offset) {
                                size_t temp = (offset == 3) ? seqState->prevOffset[0] - 1 : seqState->prevOffset[offset];
                                temp += !temp; /* 0 is not valid; input is corrupted; force offset to 1 */
                                if (offset != 1)
                                        seqState->prevOffset[2] = seqState->prevOffset[1];
                                seqState->prevOffset[1] = seqState->prevOffset[0];
                                seqState->prevOffset[0] = offset = temp;
                        } else {
                                offset = seqState->prevOffset[0];
                        }
                } else {
                        seqState->prevOffset[2] = seqState->prevOffset[1];
                        seqState->prevOffset[1] = seqState->prevOffset[0];
                        seqState->prevOffset[0] = offset;
                }
                seq.offset = offset;
        }

        seq.matchLength = ML_base[mlCode] + ((mlCode > 31) ? BIT_readBitsFast(&seqState->DStream, mlBits) : 0); /* <=  16 bits */
        if (ZSTD_32bits() && (mlBits + llBits > 24))
                BIT_reloadDStream(&seqState->DStream);

        seq.litLength = LL_base[llCode] + ((llCode > 15) ? BIT_readBitsFast(&seqState->DStream, llBits) : 0); /* <=  16 bits */
        if (ZSTD_32bits() || (totalBits > 64 - 7 - (LLFSELog + MLFSELog + OffFSELog)))
                BIT_reloadDStream(&seqState->DStream);

        {
                size_t const pos = seqState->pos + seq.litLength;
                seq.match = seqState->base + pos - seq.offset; /* single memory segment */
                if (seq.offset > pos)
                        seq.match += seqState->gotoDict; /* separate memory segment */
                seqState->pos = pos + seq.matchLength;
        }

        /* ANS state update */
        FSE_updateState(&seqState->stateLL, &seqState->DStream); /* <=  9 bits */
        FSE_updateState(&seqState->stateML, &seqState->DStream); /* <=  9 bits */
        if (ZSTD_32bits())
                BIT_reloadDStream(&seqState->DStream);             /* <= 18 bits */
        FSE_updateState(&seqState->stateOffb, &seqState->DStream); /* <=  8 bits */

        return seq;
}

static seq_t ZSTD_decodeSequenceLong(seqState_t *seqState, unsigned const windowSize)
{
        if (ZSTD_highbit32(windowSize) > STREAM_ACCUMULATOR_MIN) {
                return ZSTD_decodeSequenceLong_generic(seqState, 1);
        } else {
                return ZSTD_decodeSequenceLong_generic(seqState, 0);
        }
}

FORCE_INLINE
size_t ZSTD_execSequenceLong(BYTE *op, BYTE *const oend, seq_t sequence, const BYTE **litPtr, const BYTE *const litLimit, const BYTE *const base,
                             const BYTE *const vBase, const BYTE *const dictEnd)
{
        BYTE *const oLitEnd = op + sequence.litLength;
        size_t const sequenceLength = sequence.litLength + sequence.matchLength;
        BYTE *const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
        BYTE *const oend_w = oend - WILDCOPY_OVERLENGTH;
        const BYTE *const iLitEnd = *litPtr + sequence.litLength;
        const BYTE *match = sequence.match;

        /* check */
        if (oMatchEnd > oend)
                return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend */
        if (iLitEnd > litLimit)
                return ERROR(corruption_detected); /* over-read beyond lit buffer */
        if (oLitEnd > oend_w)
                return ZSTD_execSequenceLast7(op, oend, sequence, litPtr, litLimit, base, vBase, dictEnd);

        /* copy Literals */
        ZSTD_copy8(op, *litPtr);
        if (sequence.litLength > 8)
                ZSTD_wildcopy(op + 8, (*litPtr) + 8,
                              sequence.litLength - 8); /* note : since oLitEnd <= oend-WILDCOPY_OVERLENGTH, no risk of overwrite beyond oend */
        op = oLitEnd;
        *litPtr = iLitEnd; /* update for next sequence */

        /* copy Match */
        if (sequence.offset > (size_t)(oLitEnd - base)) {
                /* offset beyond prefix */
                if (sequence.offset > (size_t)(oLitEnd - vBase))
                        return ERROR(corruption_detected);
                if (match + sequence.matchLength <= dictEnd) {
                        memmove(oLitEnd, match, sequence.matchLength);
                        return sequenceLength;
                }
                /* span extDict & currPrefixSegment */
                {
                        size_t const length1 = dictEnd - match;
                        memmove(oLitEnd, match, length1);
                        op = oLitEnd + length1;
                        sequence.matchLength -= length1;
                        match = base;
                        if (op > oend_w || sequence.matchLength < MINMATCH) {
                                U32 i;
                                for (i = 0; i < sequence.matchLength; ++i)
                                        op[i] = match[i];
                                return sequenceLength;
                        }
                }
        }
        /* Requirement: op <= oend_w && sequence.matchLength >= MINMATCH */

        /* match within prefix */
        if (sequence.offset < 8) {
                /* close range match, overlap */
                static const U32 dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4};   /* added */
                static const int dec64table[] = {8, 8, 8, 7, 8, 9, 10, 11}; /* subtracted */
                int const sub2 = dec64table[sequence.offset];
                op[0] = match[0];
                op[1] = match[1];
                op[2] = match[2];
                op[3] = match[3];
                match += dec32table[sequence.offset];
                ZSTD_copy4(op + 4, match);
                match -= sub2;
        } else {
                ZSTD_copy8(op, match);
        }
        op += 8;
        match += 8;

        if (oMatchEnd > oend - (16 - MINMATCH)) {
                if (op < oend_w) {
                        ZSTD_wildcopy(op, match, oend_w - op);
                        match += oend_w - op;
                        op = oend_w;
                }
                while (op < oMatchEnd)
                        *op++ = *match++;
        } else {
                ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength - 8); /* works even if matchLength < 8 */
        }
        return sequenceLength;
}

static size_t ZSTD_decompressSequencesLong(ZSTD_DCtx *dctx, void *dst, size_t maxDstSize, const void *seqStart, size_t seqSize)
{
        const BYTE *ip = (const BYTE *)seqStart;
        const BYTE *const iend = ip + seqSize;
        BYTE *const ostart = (BYTE * const)dst;
        BYTE *const oend = ostart + maxDstSize;
        BYTE *op = ostart;
        const BYTE *litPtr = dctx->litPtr;
        const BYTE *const litEnd = litPtr + dctx->litSize;
        const BYTE *const base = (const BYTE *)(dctx->base);
        const BYTE *const vBase = (const BYTE *)(dctx->vBase);
        const BYTE *const dictEnd = (const BYTE *)(dctx->dictEnd);
        unsigned const windowSize = dctx->fParams.windowSize;
        int nbSeq;

        /* Build Decoding Tables */
        {
                size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, seqSize);
                if (ZSTD_isError(seqHSize))
                        return seqHSize;
                ip += seqHSize;
        }

        /* Regen sequences */
        if (nbSeq) {
#define STORED_SEQS 4
#define STOSEQ_MASK (STORED_SEQS - 1)
#define ADVANCED_SEQS 4
                seq_t *sequences = (seq_t *)dctx->entropy.workspace;
                int const seqAdvance = MIN(nbSeq, ADVANCED_SEQS);
                seqState_t seqState;
                int seqNb;
                ZSTD_STATIC_ASSERT(sizeof(dctx->entropy.workspace) >= sizeof(seq_t) * STORED_SEQS);
                dctx->fseEntropy = 1;
                {
                        U32 i;
                        for (i = 0; i < ZSTD_REP_NUM; i++)
                                seqState.prevOffset[i] = dctx->entropy.rep[i];
                }
                seqState.base = base;
                seqState.pos = (size_t)(op - base);
                seqState.gotoDict = (uPtrDiff)dictEnd - (uPtrDiff)base; /* cast to avoid undefined behaviour */
                CHECK_E(BIT_initDStream(&seqState.DStream, ip, iend - ip), corruption_detected);
                FSE_initDState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr);
                FSE_initDState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr);
                FSE_initDState(&seqState.stateML, &seqState.DStream, dctx->MLTptr);

                /* prepare in advance */
                for (seqNb = 0; (BIT_reloadDStream(&seqState.DStream) <= BIT_DStream_completed) && seqNb < seqAdvance; seqNb++) {
                        sequences[seqNb] = ZSTD_decodeSequenceLong(&seqState, windowSize);
                }
                if (seqNb < seqAdvance)
                        return ERROR(corruption_detected);

                /* decode and decompress */
                for (; (BIT_reloadDStream(&(seqState.DStream)) <= BIT_DStream_completed) && seqNb < nbSeq; seqNb++) {
                        seq_t const sequence = ZSTD_decodeSequenceLong(&seqState, windowSize);
                        size_t const oneSeqSize =
                            ZSTD_execSequenceLong(op, oend, sequences[(seqNb - ADVANCED_SEQS) & STOSEQ_MASK], &litPtr, litEnd, base, vBase, dictEnd);
                        if (ZSTD_isError(oneSeqSize))
                                return oneSeqSize;
                        ZSTD_PREFETCH(sequence.match);
                        sequences[seqNb & STOSEQ_MASK] = sequence;
                        op += oneSeqSize;
                }
                if (seqNb < nbSeq)
                        return ERROR(corruption_detected);

                /* finish queue */
                seqNb -= seqAdvance;
                for (; seqNb < nbSeq; seqNb++) {
                        size_t const oneSeqSize = ZSTD_execSequenceLong(op, oend, sequences[seqNb & STOSEQ_MASK], &litPtr, litEnd, base, vBase, dictEnd);
                        if (ZSTD_isError(oneSeqSize))
                                return oneSeqSize;
                        op += oneSeqSize;
                }

                /* save reps for next block */
                {
                        U32 i;
                        for (i = 0; i < ZSTD_REP_NUM; i++)
                                dctx->entropy.rep[i] = (U32)(seqState.prevOffset[i]);
                }
        }

        /* last literal segment */
        {
                size_t const lastLLSize = litEnd - litPtr;
                if (lastLLSize > (size_t)(oend - op))
                        return ERROR(dstSize_tooSmall);
                memcpy(op, litPtr, lastLLSize);
                op += lastLLSize;
        }

        return op - ostart;
}

static size_t ZSTD_decompressBlock_internal(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize)
{ /* blockType == blockCompressed */
        const BYTE *ip = (const BYTE *)src;

        if (srcSize >= ZSTD_BLOCKSIZE_ABSOLUTEMAX)
                return ERROR(srcSize_wrong);

        /* Decode literals section */
        {
                size_t const litCSize = ZSTD_decodeLiteralsBlock(dctx, src, srcSize);
                if (ZSTD_isError(litCSize))
                        return litCSize;
                ip += litCSize;
                srcSize -= litCSize;
        }
        if (sizeof(size_t) > 4) /* do not enable prefetching on 32-bits x86, as it's performance detrimental */
                                /* likely because of register pressure */
                                /* if that's the correct cause, then 32-bits ARM should be affected differently */
                                /* it would be good to test this on ARM real hardware, to see if prefetch version improves speed */
                if (dctx->fParams.windowSize > (1 << 23))
                        return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize);
        return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize);
}

static void ZSTD_checkContinuity(ZSTD_DCtx *dctx, const void *dst)
{
        if (dst != dctx->previousDstEnd) { /* not contiguous */
                dctx->dictEnd = dctx->previousDstEnd;
                dctx->vBase = (const char *)dst - ((const char *)(dctx->previousDstEnd) - (const char *)(dctx->base));
                dctx->base = dst;
                dctx->previousDstEnd = dst;
        }
}

size_t ZSTD_decompressBlock(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize)
{
        size_t dSize;
        ZSTD_checkContinuity(dctx, dst);
        dSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize);
        dctx->previousDstEnd = (char *)dst + dSize;
        return dSize;
}

/** ZSTD_insertBlock() :
        insert `src` block into `dctx` history. Useful to track uncompressed blocks. */
size_t ZSTD_insertBlock(ZSTD_DCtx *dctx, const void *blockStart, size_t blockSize)
{
        ZSTD_checkContinuity(dctx, blockStart);
        dctx->previousDstEnd = (const char *)blockStart + blockSize;
        return blockSize;
}

size_t ZSTD_generateNxBytes(void *dst, size_t dstCapacity, BYTE byte, size_t length)
{
        if (length > dstCapacity)
                return ERROR(dstSize_tooSmall);
        memset(dst, byte, length);
        return length;
}

/** ZSTD_findFrameCompressedSize() :
 *  compatible with legacy mode
 *  `src` must point to the start of a ZSTD frame, ZSTD legacy frame, or skippable frame
 *  `srcSize` must be at least as large as the frame contained
 *  @return : the compressed size of the frame starting at `src` */
size_t ZSTD_findFrameCompressedSize(const void *src, size_t srcSize)
{
        if (srcSize >= ZSTD_skippableHeaderSize && (ZSTD_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
                return ZSTD_skippableHeaderSize + ZSTD_readLE32((const BYTE *)src + 4);
        } else {
                const BYTE *ip = (const BYTE *)src;
                const BYTE *const ipstart = ip;
                size_t remainingSize = srcSize;
                ZSTD_frameParams fParams;

                size_t const headerSize = ZSTD_frameHeaderSize(ip, remainingSize);
                if (ZSTD_isError(headerSize))
                        return headerSize;

                /* Frame Header */
                {
                        size_t const ret = ZSTD_getFrameParams(&fParams, ip, remainingSize);
                        if (ZSTD_isError(ret))
                                return ret;
                        if (ret > 0)
                                return ERROR(srcSize_wrong);
                }

                ip += headerSize;
                remainingSize -= headerSize;

                /* Loop on each block */
                while (1) {
                        blockProperties_t blockProperties;
                        size_t const cBlockSize = ZSTD_getcBlockSize(ip, remainingSize, &blockProperties);
                        if (ZSTD_isError(cBlockSize))
                                return cBlockSize;

                        if (ZSTD_blockHeaderSize + cBlockSize > remainingSize)
                                return ERROR(srcSize_wrong);

                        ip += ZSTD_blockHeaderSize + cBlockSize;
                        remainingSize -= ZSTD_blockHeaderSize + cBlockSize;

                        if (blockProperties.lastBlock)
                                break;
                }

                if (fParams.checksumFlag) { /* Frame content checksum */
                        if (remainingSize < 4)
                                return ERROR(srcSize_wrong);
                        ip += 4;
                        remainingSize -= 4;
                }

                return ip - ipstart;
        }
}

/*! ZSTD_decompressFrame() :
*   @dctx must be properly initialized */
static size_t ZSTD_decompressFrame(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void **srcPtr, size_t *srcSizePtr)
{
        const BYTE *ip = (const BYTE *)(*srcPtr);
        BYTE *const ostart = (BYTE * const)dst;
        BYTE *const oend = ostart + dstCapacity;
        BYTE *op = ostart;
        size_t remainingSize = *srcSizePtr;

        /* check */
        if (remainingSize < ZSTD_frameHeaderSize_min + ZSTD_blockHeaderSize)
                return ERROR(srcSize_wrong);

        /* Frame Header */
        {
                size_t const frameHeaderSize = ZSTD_frameHeaderSize(ip, ZSTD_frameHeaderSize_prefix);
                if (ZSTD_isError(frameHeaderSize))
                        return frameHeaderSize;
                if (remainingSize < frameHeaderSize + ZSTD_blockHeaderSize)
                        return ERROR(srcSize_wrong);
                CHECK_F(ZSTD_decodeFrameHeader(dctx, ip, frameHeaderSize));
                ip += frameHeaderSize;
                remainingSize -= frameHeaderSize;
        }

        /* Loop on each block */
        while (1) {
                size_t decodedSize;
                blockProperties_t blockProperties;
                size_t const cBlockSize = ZSTD_getcBlockSize(ip, remainingSize, &blockProperties);
                if (ZSTD_isError(cBlockSize))
                        return cBlockSize;

                ip += ZSTD_blockHeaderSize;
                remainingSize -= ZSTD_blockHeaderSize;
                if (cBlockSize > remainingSize)
                        return ERROR(srcSize_wrong);

                switch (blockProperties.blockType) {
                case bt_compressed: decodedSize = ZSTD_decompressBlock_internal(dctx, op, oend - op, ip, cBlockSize); break;
                case bt_raw: decodedSize = ZSTD_copyRawBlock(op, oend - op, ip, cBlockSize); break;
                case bt_rle: decodedSize = ZSTD_generateNxBytes(op, oend - op, *ip, blockProperties.origSize); break;
                case bt_reserved:
                default: return ERROR(corruption_detected);
                }

                if (ZSTD_isError(decodedSize))
                        return decodedSize;
                if (dctx->fParams.checksumFlag)
                        xxh64_update(&dctx->xxhState, op, decodedSize);
                op += decodedSize;
                ip += cBlockSize;
                remainingSize -= cBlockSize;
                if (blockProperties.lastBlock)
                        break;
        }

        if (dctx->fParams.checksumFlag) { /* Frame content checksum verification */
                U32 const checkCalc = (U32)xxh64_digest(&dctx->xxhState);
                U32 checkRead;
                if (remainingSize < 4)
                        return ERROR(checksum_wrong);
                checkRead = ZSTD_readLE32(ip);
                if (checkRead != checkCalc)
                        return ERROR(checksum_wrong);
                ip += 4;
                remainingSize -= 4;
        }

        /* Allow caller to get size read */
        *srcPtr = ip;
        *srcSizePtr = remainingSize;
        return op - ostart;
}

static const void *ZSTD_DDictDictContent(const ZSTD_DDict *ddict);
static size_t ZSTD_DDictDictSize(const ZSTD_DDict *ddict);

static size_t ZSTD_decompressMultiFrame(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize, const void *dict, size_t dictSize,
                                        const ZSTD_DDict *ddict)
{
        void *const dststart = dst;

        if (ddict) {
                if (dict) {
                        /* programmer error, these two cases should be mutually exclusive */
                        return ERROR(GENERIC);
                }

                dict = ZSTD_DDictDictContent(ddict);
                dictSize = ZSTD_DDictDictSize(ddict);
        }

        while (srcSize >= ZSTD_frameHeaderSize_prefix) {
                U32 magicNumber;

                magicNumber = ZSTD_readLE32(src);
                if (magicNumber != ZSTD_MAGICNUMBER) {
                        if ((magicNumber & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
                                size_t skippableSize;
                                if (srcSize < ZSTD_skippableHeaderSize)
                                        return ERROR(srcSize_wrong);
                                skippableSize = ZSTD_readLE32((const BYTE *)src + 4) + ZSTD_skippableHeaderSize;
                                if (srcSize < skippableSize) {
                                        return ERROR(srcSize_wrong);
                                }

                                src = (const BYTE *)src + skippableSize;
                                srcSize -= skippableSize;
                                continue;
                        } else {
                                return ERROR(prefix_unknown);
                        }
                }

                if (ddict) {
                        /* we were called from ZSTD_decompress_usingDDict */
                        ZSTD_refDDict(dctx, ddict);
                } else {
                        /* this will initialize correctly with no dict if dict == NULL, so
                         * use this in all cases but ddict */
                        CHECK_F(ZSTD_decompressBegin_usingDict(dctx, dict, dictSize));
                }
                ZSTD_checkContinuity(dctx, dst);

                {
                        const size_t res = ZSTD_decompressFrame(dctx, dst, dstCapacity, &src, &srcSize);
                        if (ZSTD_isError(res))
                                return res;
                        /* don't need to bounds check this, ZSTD_decompressFrame will have
                         * already */
                        dst = (BYTE *)dst + res;
                        dstCapacity -= res;
                }
        }

        if (srcSize)
                return ERROR(srcSize_wrong); /* input not entirely consumed */

        return (BYTE *)dst - (BYTE *)dststart;
}

size_t ZSTD_decompress_usingDict(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize, const void *dict, size_t dictSize)
{
        return ZSTD_decompressMultiFrame(dctx, dst, dstCapacity, src, srcSize, dict, dictSize, NULL);
}

size_t ZSTD_decompressDCtx(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize)
{
        return ZSTD_decompress_usingDict(dctx, dst, dstCapacity, src, srcSize, NULL, 0);
}

/*-**************************************
*   Advanced Streaming Decompression API
*   Bufferless and synchronous
****************************************/
size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx *dctx) { return dctx->expected; }

ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx *dctx)
{
        switch (dctx->stage) {
        default: /* should not happen */
        case ZSTDds_getFrameHeaderSize:
        case ZSTDds_decodeFrameHeader: return ZSTDnit_frameHeader;
        case ZSTDds_decodeBlockHeader: return ZSTDnit_blockHeader;
        case ZSTDds_decompressBlock: return ZSTDnit_block;
        case ZSTDds_decompressLastBlock: return ZSTDnit_lastBlock;
        case ZSTDds_checkChecksum: return ZSTDnit_checksum;
        case ZSTDds_decodeSkippableHeader:
        case ZSTDds_skipFrame: return ZSTDnit_skippableFrame;
        }
}

int ZSTD_isSkipFrame(ZSTD_DCtx *dctx) { return dctx->stage == ZSTDds_skipFrame; } /* for zbuff */

/** ZSTD_decompressContinue() :
*   @return : nb of bytes generated into `dst` (necessarily <= `dstCapacity)
*             or an error code, which can be tested using ZSTD_isError() */
size_t ZSTD_decompressContinue(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize)
{
        /* Sanity check */
        if (srcSize != dctx->expected)
                return ERROR(srcSize_wrong);
        if (dstCapacity)
                ZSTD_checkContinuity(dctx, dst);

        switch (dctx->stage) {
        case ZSTDds_getFrameHeaderSize:
                if (srcSize != ZSTD_frameHeaderSize_prefix)
                        return ERROR(srcSize_wrong);                                    /* impossible */
                if ((ZSTD_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) { /* skippable frame */
                        memcpy(dctx->headerBuffer, src, ZSTD_frameHeaderSize_prefix);
                        dctx->expected = ZSTD_skippableHeaderSize - ZSTD_frameHeaderSize_prefix; /* magic number + skippable frame length */
                        dctx->stage = ZSTDds_decodeSkippableHeader;
                        return 0;
                }
                dctx->headerSize = ZSTD_frameHeaderSize(src, ZSTD_frameHeaderSize_prefix);
                if (ZSTD_isError(dctx->headerSize))
                        return dctx->headerSize;
                memcpy(dctx->headerBuffer, src, ZSTD_frameHeaderSize_prefix);
                if (dctx->headerSize > ZSTD_frameHeaderSize_prefix) {
                        dctx->expected = dctx->headerSize - ZSTD_frameHeaderSize_prefix;
                        dctx->stage = ZSTDds_decodeFrameHeader;
                        return 0;
                }
                dctx->expected = 0; /* not necessary to copy more */

        case ZSTDds_decodeFrameHeader:
                memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_prefix, src, dctx->expected);
                CHECK_F(ZSTD_decodeFrameHeader(dctx, dctx->headerBuffer, dctx->headerSize));
                dctx->expected = ZSTD_blockHeaderSize;
                dctx->stage = ZSTDds_decodeBlockHeader;
                return 0;

        case ZSTDds_decodeBlockHeader: {
                blockProperties_t bp;
                size_t const cBlockSize = ZSTD_getcBlockSize(src, ZSTD_blockHeaderSize, &bp);
                if (ZSTD_isError(cBlockSize))
                        return cBlockSize;
                dctx->expected = cBlockSize;
                dctx->bType = bp.blockType;
                dctx->rleSize = bp.origSize;
                if (cBlockSize) {
                        dctx->stage = bp.lastBlock ? ZSTDds_decompressLastBlock : ZSTDds_decompressBlock;
                        return 0;
                }
                /* empty block */
                if (bp.lastBlock) {
                        if (dctx->fParams.checksumFlag) {
                                dctx->expected = 4;
                                dctx->stage = ZSTDds_checkChecksum;
                        } else {
                                dctx->expected = 0; /* end of frame */
                                dctx->stage = ZSTDds_getFrameHeaderSize;
                        }
                } else {
                        dctx->expected = 3; /* go directly to next header */
                        dctx->stage = ZSTDds_decodeBlockHeader;
                }
                return 0;
        }
        case ZSTDds_decompressLastBlock:
        case ZSTDds_decompressBlock: {
                size_t rSize;
                switch (dctx->bType) {
                case bt_compressed: rSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize); break;
                case bt_raw: rSize = ZSTD_copyRawBlock(dst, dstCapacity, src, srcSize); break;
                case bt_rle: rSize = ZSTD_setRleBlock(dst, dstCapacity, src, srcSize, dctx->rleSize); break;
                case bt_reserved: /* should never happen */
                default: return ERROR(corruption_detected);
                }
                if (ZSTD_isError(rSize))
                        return rSize;
                if (dctx->fParams.checksumFlag)
                        xxh64_update(&dctx->xxhState, dst, rSize);

                if (dctx->stage == ZSTDds_decompressLastBlock) { /* end of frame */
                        if (dctx->fParams.checksumFlag) {       /* another round for frame checksum */
                                dctx->expected = 4;
                                dctx->stage = ZSTDds_checkChecksum;
                        } else {
                                dctx->expected = 0; /* ends here */
                                dctx->stage = ZSTDds_getFrameHeaderSize;
                        }
                } else {
                        dctx->stage = ZSTDds_decodeBlockHeader;
                        dctx->expected = ZSTD_blockHeaderSize;
                        dctx->previousDstEnd = (char *)dst + rSize;
                }
                return rSize;
        }
        case ZSTDds_checkChecksum: {
                U32 const h32 = (U32)xxh64_digest(&dctx->xxhState);
                U32 const check32 = ZSTD_readLE32(src); /* srcSize == 4, guaranteed by dctx->expected */
                if (check32 != h32)
                        return ERROR(checksum_wrong);
                dctx->expected = 0;
                dctx->stage = ZSTDds_getFrameHeaderSize;
                return 0;
        }
        case ZSTDds_decodeSkippableHeader: {
                memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_prefix, src, dctx->expected);
                dctx->expected = ZSTD_readLE32(dctx->headerBuffer + 4);
                dctx->stage = ZSTDds_skipFrame;
                return 0;
        }
        case ZSTDds_skipFrame: {
                dctx->expected = 0;
                dctx->stage = ZSTDds_getFrameHeaderSize;
                return 0;
        }
        default:
                return ERROR(GENERIC); /* impossible */
        }
}

static size_t ZSTD_refDictContent(ZSTD_DCtx *dctx, const void *dict, size_t dictSize)
{
        dctx->dictEnd = dctx->previousDstEnd;
        dctx->vBase = (const char *)dict - ((const char *)(dctx->previousDstEnd) - (const char *)(dctx->base));
        dctx->base = dict;
        dctx->previousDstEnd = (const char *)dict + dictSize;
        return 0;
}

/* ZSTD_loadEntropy() :
 * dict : must point at beginning of a valid zstd dictionary
 * @return : size of entropy tables read */
static size_t ZSTD_loadEntropy(ZSTD_entropyTables_t *entropy, const void *const dict, size_t const dictSize)
{
        const BYTE *dictPtr = (const BYTE *)dict;
        const BYTE *const dictEnd = dictPtr + dictSize;

        if (dictSize <= 8)
                return ERROR(dictionary_corrupted);
        dictPtr += 8; /* skip header = magic + dictID */

        {
                size_t const hSize = HUF_readDTableX4_wksp(entropy->hufTable, dictPtr, dictEnd - dictPtr, entropy->workspace, sizeof(entropy->workspace));
                if (HUF_isError(hSize))
                        return ERROR(dictionary_corrupted);
                dictPtr += hSize;
        }

        {
                short offcodeNCount[MaxOff + 1];
                U32 offcodeMaxValue = MaxOff, offcodeLog;
                size_t const offcodeHeaderSize = FSE_readNCount(offcodeNCount, &offcodeMaxValue, &offcodeLog, dictPtr, dictEnd - dictPtr);
                if (FSE_isError(offcodeHeaderSize))
                        return ERROR(dictionary_corrupted);
                if (offcodeLog > OffFSELog)
                        return ERROR(dictionary_corrupted);
                CHECK_E(FSE_buildDTable_wksp(entropy->OFTable, offcodeNCount, offcodeMaxValue, offcodeLog, entropy->workspace, sizeof(entropy->workspace)), dictionary_corrupted);
                dictPtr += offcodeHeaderSize;
        }

        {
                short matchlengthNCount[MaxML + 1];
                unsigned matchlengthMaxValue = MaxML, matchlengthLog;
                size_t const matchlengthHeaderSize = FSE_readNCount(matchlengthNCount, &matchlengthMaxValue, &matchlengthLog, dictPtr, dictEnd - dictPtr);
                if (FSE_isError(matchlengthHeaderSize))
                        return ERROR(dictionary_corrupted);
                if (matchlengthLog > MLFSELog)
                        return ERROR(dictionary_corrupted);
                CHECK_E(FSE_buildDTable_wksp(entropy->MLTable, matchlengthNCount, matchlengthMaxValue, matchlengthLog, entropy->workspace, sizeof(entropy->workspace)), dictionary_corrupted);
                dictPtr += matchlengthHeaderSize;
        }

        {
                short litlengthNCount[MaxLL + 1];
                unsigned litlengthMaxValue = MaxLL, litlengthLog;
                size_t const litlengthHeaderSize = FSE_readNCount(litlengthNCount, &litlengthMaxValue, &litlengthLog, dictPtr, dictEnd - dictPtr);
                if (FSE_isError(litlengthHeaderSize))
                        return ERROR(dictionary_corrupted);
                if (litlengthLog > LLFSELog)
                        return ERROR(dictionary_corrupted);
                CHECK_E(FSE_buildDTable_wksp(entropy->LLTable, litlengthNCount, litlengthMaxValue, litlengthLog, entropy->workspace, sizeof(entropy->workspace)), dictionary_corrupted);
                dictPtr += litlengthHeaderSize;
        }

        if (dictPtr + 12 > dictEnd)
                return ERROR(dictionary_corrupted);
        {
                int i;
                size_t const dictContentSize = (size_t)(dictEnd - (dictPtr + 12));
                for (i = 0; i < 3; i++) {
                        U32 const rep = ZSTD_readLE32(dictPtr);
                        dictPtr += 4;
                        if (rep == 0 || rep >= dictContentSize)
                                return ERROR(dictionary_corrupted);
                        entropy->rep[i] = rep;
                }
        }

        return dictPtr - (const BYTE *)dict;
}

static size_t ZSTD_decompress_insertDictionary(ZSTD_DCtx *dctx, const void *dict, size_t dictSize)
{
        if (dictSize < 8)
                return ZSTD_refDictContent(dctx, dict, dictSize);
        {
                U32 const magic = ZSTD_readLE32(dict);
                if (magic != ZSTD_DICT_MAGIC) {
                        return ZSTD_refDictContent(dctx, dict, dictSize); /* pure content mode */
                }
        }
        dctx->dictID = ZSTD_readLE32((const char *)dict + 4);

        /* load entropy tables */
        {
                size_t const eSize = ZSTD_loadEntropy(&dctx->entropy, dict, dictSize);
                if (ZSTD_isError(eSize))
                        return ERROR(dictionary_corrupted);
                dict = (const char *)dict + eSize;
                dictSize -= eSize;
        }
        dctx->litEntropy = dctx->fseEntropy = 1;

        /* reference dictionary content */
        return ZSTD_refDictContent(dctx, dict, dictSize);
}

size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx *dctx, const void *dict, size_t dictSize)
{
        CHECK_F(ZSTD_decompressBegin(dctx));
        if (dict && dictSize)
                CHECK_E(ZSTD_decompress_insertDictionary(dctx, dict, dictSize), dictionary_corrupted);
        return 0;
}

/* ======   ZSTD_DDict   ====== */

struct ZSTD_DDict_s {
        void *dictBuffer;
        const void *dictContent;
        size_t dictSize;
        ZSTD_entropyTables_t entropy;
        U32 dictID;
        U32 entropyPresent;
        ZSTD_customMem cMem;
}; /* typedef'd to ZSTD_DDict within "zstd.h" */

size_t ZSTD_DDictWorkspaceBound(void) { return ZSTD_ALIGN(sizeof(ZSTD_stack)) + ZSTD_ALIGN(sizeof(ZSTD_DDict)); }

static const void *ZSTD_DDictDictContent(const ZSTD_DDict *ddict) { return ddict->dictContent; }

static size_t ZSTD_DDictDictSize(const ZSTD_DDict *ddict) { return ddict->dictSize; }

static void ZSTD_refDDict(ZSTD_DCtx *dstDCtx, const ZSTD_DDict *ddict)
{
        ZSTD_decompressBegin(dstDCtx); /* init */
        if (ddict) {                   /* support refDDict on NULL */
                dstDCtx->dictID = ddict->dictID;
                dstDCtx->base = ddict->dictContent;
                dstDCtx->vBase = ddict->dictContent;
                dstDCtx->dictEnd = (const BYTE *)ddict->dictContent + ddict->dictSize;
                dstDCtx->previousDstEnd = dstDCtx->dictEnd;
                if (ddict->entropyPresent) {
                        dstDCtx->litEntropy = 1;
                        dstDCtx->fseEntropy = 1;
                        dstDCtx->LLTptr = ddict->entropy.LLTable;
                        dstDCtx->MLTptr = ddict->entropy.MLTable;
                        dstDCtx->OFTptr = ddict->entropy.OFTable;
                        dstDCtx->HUFptr = ddict->entropy.hufTable;

                        dstDCtx->entropy.rep[0] = ddict->entropy.rep[0];
                        dstDCtx->entropy.rep[1] = ddict->entropy.rep[1];
                        dstDCtx->entropy.rep[2] = ddict->entropy.rep[2];
                } else {
                        dstDCtx->litEntropy = 0;
                        dstDCtx->fseEntropy = 0;
                }
        }
}

static size_t ZSTD_loadEntropy_inDDict(ZSTD_DDict *ddict)
{
        ddict->dictID = 0;
        ddict->entropyPresent = 0;
        if (ddict->dictSize < 8)
                return 0;
        {
                U32 const magic = ZSTD_readLE32(ddict->dictContent);
                if (magic != ZSTD_DICT_MAGIC)
                        return 0; /* pure content mode */
        }
        ddict->dictID = ZSTD_readLE32((const char *)ddict->dictContent + 4);

        /* load entropy tables */
        CHECK_E(ZSTD_loadEntropy(&ddict->entropy, ddict->dictContent, ddict->dictSize), dictionary_corrupted);
        ddict->entropyPresent = 1;
        return 0;
}

static ZSTD_DDict *ZSTD_createDDict_advanced(const void *dict, size_t dictSize, unsigned byReference, ZSTD_customMem customMem)
{
        if (!customMem.customAlloc || !customMem.customFree)
                return NULL;

        {
                ZSTD_DDict *const ddict = (ZSTD_DDict *)ZSTD_malloc(sizeof(ZSTD_DDict), customMem);
                if (!ddict)
                        return NULL;
                ddict->cMem = customMem;

                if ((byReference) || (!dict) || (!dictSize)) {
                        ddict->dictBuffer = NULL;
                        ddict->dictContent = dict;
                } else {
                        void *const internalBuffer = ZSTD_malloc(dictSize, customMem);
                        if (!internalBuffer) {
                                ZSTD_freeDDict(ddict);
                                return NULL;
                        }
                        memcpy(internalBuffer, dict, dictSize);
                        ddict->dictBuffer = internalBuffer;
                        ddict->dictContent = internalBuffer;
                }
                ddict->dictSize = dictSize;
                ddict->entropy.hufTable[0] = (HUF_DTable)((HufLog)*0x1000001); /* cover both little and big endian */
                /* parse dictionary content */
                {
                        size_t const errorCode = ZSTD_loadEntropy_inDDict(ddict);
                        if (ZSTD_isError(errorCode)) {
                                ZSTD_freeDDict(ddict);
                                return NULL;
                        }
                }

                return ddict;
        }
}

/*! ZSTD_initDDict() :
*   Create a digested dictionary, to start decompression without startup delay.
*   `dict` content is copied inside DDict.
*   Consequently, `dict` can be released after `ZSTD_DDict` creation */
ZSTD_DDict *ZSTD_initDDict(const void *dict, size_t dictSize, void *workspace, size_t workspaceSize)
{
        ZSTD_customMem const stackMem = ZSTD_initStack(workspace, workspaceSize);
        return ZSTD_createDDict_advanced(dict, dictSize, 1, stackMem);
}

size_t ZSTD_freeDDict(ZSTD_DDict *ddict)
{
        if (ddict == NULL)
                return 0; /* support free on NULL */
        {
                ZSTD_customMem const cMem = ddict->cMem;
                ZSTD_free(ddict->dictBuffer, cMem);
                ZSTD_free(ddict, cMem);
                return 0;
        }
}

/*! ZSTD_getDictID_fromDict() :
 *  Provides the dictID stored within dictionary.
 *  if @return == 0, the dictionary is not conformant with Zstandard specification.
 *  It can still be loaded, but as a content-only dictionary. */
unsigned ZSTD_getDictID_fromDict(const void *dict, size_t dictSize)
{
        if (dictSize < 8)
                return 0;
        if (ZSTD_readLE32(dict) != ZSTD_DICT_MAGIC)
                return 0;
        return ZSTD_readLE32((const char *)dict + 4);
}

/*! ZSTD_getDictID_fromDDict() :
 *  Provides the dictID of the dictionary loaded into `ddict`.
 *  If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
 *  Non-conformant dictionaries can still be loaded, but as content-only dictionaries. */
unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict *ddict)
{
        if (ddict == NULL)
                return 0;
        return ZSTD_getDictID_fromDict(ddict->dictContent, ddict->dictSize);
}

/*! ZSTD_getDictID_fromFrame() :
 *  Provides the dictID required to decompressed the frame stored within `src`.
 *  If @return == 0, the dictID could not be decoded.
 *  This could for one of the following reasons :
 *  - The frame does not require a dictionary to be decoded (most common case).
 *  - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
 *    Note : this use case also happens when using a non-conformant dictionary.
 *  - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
 *  - This is not a Zstandard frame.
 *  When identifying the exact failure cause, it's possible to used ZSTD_getFrameParams(), which will provide a more precise error code. */
unsigned ZSTD_getDictID_fromFrame(const void *src, size_t srcSize)
{
        ZSTD_frameParams zfp = {0, 0, 0, 0};
        size_t const hError = ZSTD_getFrameParams(&zfp, src, srcSize);
        if (ZSTD_isError(hError))
                return 0;
        return zfp.dictID;
}

/*! ZSTD_decompress_usingDDict() :
*   Decompression using a pre-digested Dictionary
*   Use dictionary without significant overhead. */
size_t ZSTD_decompress_usingDDict(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize, const ZSTD_DDict *ddict)
{
        /* pass content and size in case legacy frames are encountered */
        return ZSTD_decompressMultiFrame(dctx, dst, dstCapacity, src, srcSize, NULL, 0, ddict);
}

/*=====================================
*   Streaming decompression
*====================================*/

typedef enum { zdss_init, zdss_loadHeader, zdss_read, zdss_load, zdss_flush } ZSTD_dStreamStage;

/* *** Resource management *** */
struct ZSTD_DStream_s {
        ZSTD_DCtx *dctx;
        ZSTD_DDict *ddictLocal;
        const ZSTD_DDict *ddict;
        ZSTD_frameParams fParams;
        ZSTD_dStreamStage stage;
        char *inBuff;
        size_t inBuffSize;
        size_t inPos;
        size_t maxWindowSize;
        char *outBuff;
        size_t outBuffSize;
        size_t outStart;
        size_t outEnd;
        size_t blockSize;
        BYTE headerBuffer[ZSTD_FRAMEHEADERSIZE_MAX]; /* tmp buffer to store frame header */
        size_t lhSize;
        ZSTD_customMem customMem;
        void *legacyContext;
        U32 previousLegacyVersion;
        U32 legacyVersion;
        U32 hostageByte;
}; /* typedef'd to ZSTD_DStream within "zstd.h" */

size_t ZSTD_DStreamWorkspaceBound(size_t maxWindowSize)
{
        size_t const blockSize = MIN(maxWindowSize, ZSTD_BLOCKSIZE_ABSOLUTEMAX);
        size_t const inBuffSize = blockSize;
        size_t const outBuffSize = maxWindowSize + blockSize + WILDCOPY_OVERLENGTH * 2;
        return ZSTD_DCtxWorkspaceBound() + ZSTD_ALIGN(sizeof(ZSTD_DStream)) + ZSTD_ALIGN(inBuffSize) + ZSTD_ALIGN(outBuffSize);
}

static ZSTD_DStream *ZSTD_createDStream_advanced(ZSTD_customMem customMem)
{
        ZSTD_DStream *zds;

        if (!customMem.customAlloc || !customMem.customFree)
                return NULL;

        zds = (ZSTD_DStream *)ZSTD_malloc(sizeof(ZSTD_DStream), customMem);
        if (zds == NULL)
                return NULL;
        memset(zds, 0, sizeof(ZSTD_DStream));
        memcpy(&zds->customMem, &customMem, sizeof(ZSTD_customMem));
        zds->dctx = ZSTD_createDCtx_advanced(customMem);
        if (zds->dctx == NULL) {
                ZSTD_freeDStream(zds);
                return NULL;
        }
        zds->stage = zdss_init;
        zds->maxWindowSize = ZSTD_MAXWINDOWSIZE_DEFAULT;
        return zds;
}

ZSTD_DStream *ZSTD_initDStream(size_t maxWindowSize, void *workspace, size_t workspaceSize)
{
        ZSTD_customMem const stackMem = ZSTD_initStack(workspace, workspaceSize);
        ZSTD_DStream *zds = ZSTD_createDStream_advanced(stackMem);
        if (!zds) {
                return NULL;
        }

        zds->maxWindowSize = maxWindowSize;
        zds->stage = zdss_loadHeader;
        zds->lhSize = zds->inPos = zds->outStart = zds->outEnd = 0;
        ZSTD_freeDDict(zds->ddictLocal);
        zds->ddictLocal = NULL;
        zds->ddict = zds->ddictLocal;
        zds->legacyVersion = 0;
        zds->hostageByte = 0;

        {
                size_t const blockSize = MIN(zds->maxWindowSize, ZSTD_BLOCKSIZE_ABSOLUTEMAX);
                size_t const neededOutSize = zds->maxWindowSize + blockSize + WILDCOPY_OVERLENGTH * 2;

                zds->inBuff = (char *)ZSTD_malloc(blockSize, zds->customMem);
                zds->inBuffSize = blockSize;
                zds->outBuff = (char *)ZSTD_malloc(neededOutSize, zds->customMem);
                zds->outBuffSize = neededOutSize;
                if (zds->inBuff == NULL || zds->outBuff == NULL) {
                        ZSTD_freeDStream(zds);
                        return NULL;
                }
        }
        return zds;
}

ZSTD_DStream *ZSTD_initDStream_usingDDict(size_t maxWindowSize, const ZSTD_DDict *ddict, void *workspace, size_t workspaceSize)
{
        ZSTD_DStream *zds = ZSTD_initDStream(maxWindowSize, workspace, workspaceSize);
        if (zds) {
                zds->ddict = ddict;
        }
        return zds;
}

size_t ZSTD_freeDStream(ZSTD_DStream *zds)
{
        if (zds == NULL)
                return 0; /* support free on null */
        {
                ZSTD_customMem const cMem = zds->customMem;
                ZSTD_freeDCtx(zds->dctx);
                zds->dctx = NULL;
                ZSTD_freeDDict(zds->ddictLocal);
                zds->ddictLocal = NULL;
                ZSTD_free(zds->inBuff, cMem);
                zds->inBuff = NULL;
                ZSTD_free(zds->outBuff, cMem);
                zds->outBuff = NULL;
                ZSTD_free(zds, cMem);
                return 0;
        }
}

/* *** Initialization *** */

size_t ZSTD_DStreamInSize(void) { return ZSTD_BLOCKSIZE_ABSOLUTEMAX + ZSTD_blockHeaderSize; }
size_t ZSTD_DStreamOutSize(void) { return ZSTD_BLOCKSIZE_ABSOLUTEMAX; }

size_t ZSTD_resetDStream(ZSTD_DStream *zds)
{
        zds->stage = zdss_loadHeader;
        zds->lhSize = zds->inPos = zds->outStart = zds->outEnd = 0;
        zds->legacyVersion = 0;
        zds->hostageByte = 0;
        return ZSTD_frameHeaderSize_prefix;
}

/* *****   Decompression   ***** */

ZSTD_STATIC size_t ZSTD_limitCopy(void *dst, size_t dstCapacity, const void *src, size_t srcSize)
{
        size_t const length = MIN(dstCapacity, srcSize);
        memcpy(dst, src, length);
        return length;
}

size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inBuffer *input)
{
        const char *const istart = (const char *)(input->src) + input->pos;
        const char *const iend = (const char *)(input->src) + input->size;
        const char *ip = istart;
        char *const ostart = (char *)(output->dst) + output->pos;
        char *const oend = (char *)(output->dst) + output->size;
        char *op = ostart;
        U32 someMoreWork = 1;

        while (someMoreWork) {
                switch (zds->stage) {
                case zdss_init:
                        ZSTD_resetDStream(zds); /* transparent reset on starting decoding a new frame */
                                                /* fall-through */

                case zdss_loadHeader: {
                        size_t const hSize = ZSTD_getFrameParams(&zds->fParams, zds->headerBuffer, zds->lhSize);
                        if (ZSTD_isError(hSize))
                                return hSize;
                        if (hSize != 0) {                                  /* need more input */
                                size_t const toLoad = hSize - zds->lhSize; /* if hSize!=0, hSize > zds->lhSize */
                                if (toLoad > (size_t)(iend - ip)) {     /* not enough input to load full header */
                                        memcpy(zds->headerBuffer + zds->lhSize, ip, iend - ip);
                                        zds->lhSize += iend - ip;
                                        input->pos = input->size;
                                        return (MAX(ZSTD_frameHeaderSize_min, hSize) - zds->lhSize) +
                                               ZSTD_blockHeaderSize; /* remaining header bytes + next block header */
                                }
                                memcpy(zds->headerBuffer + zds->lhSize, ip, toLoad);
                                zds->lhSize = hSize;
                                ip += toLoad;
                                break;
                        }

                        /* check for single-pass mode opportunity */
                        if (zds->fParams.frameContentSize && zds->fParams.windowSize /* skippable frame if == 0 */
                            && (U64)(size_t)(oend - op) >= zds->fParams.frameContentSize) {
                                size_t const cSize = ZSTD_findFrameCompressedSize(istart, iend - istart);
                                if (cSize <= (size_t)(iend - istart)) {
                                        size_t const decompressedSize = ZSTD_decompress_usingDDict(zds->dctx, op, oend - op, istart, cSize, zds->ddict);
                                        if (ZSTD_isError(decompressedSize))
                                                return decompressedSize;
                                        ip = istart + cSize;
                                        op += decompressedSize;
                                        zds->dctx->expected = 0;
                                        zds->stage = zdss_init;
                                        someMoreWork = 0;
                                        break;
                                }
                        }

                        /* Consume header */
                        ZSTD_refDDict(zds->dctx, zds->ddict);
                        {
                                size_t const h1Size = ZSTD_nextSrcSizeToDecompress(zds->dctx); /* == ZSTD_frameHeaderSize_prefix */
                                CHECK_F(ZSTD_decompressContinue(zds->dctx, NULL, 0, zds->headerBuffer, h1Size));
                                {
                                        size_t const h2Size = ZSTD_nextSrcSizeToDecompress(zds->dctx);
                                        CHECK_F(ZSTD_decompressContinue(zds->dctx, NULL, 0, zds->headerBuffer + h1Size, h2Size));
                                }
                        }

                        zds->fParams.windowSize = MAX(zds->fParams.windowSize, 1U << ZSTD_WINDOWLOG_ABSOLUTEMIN);
                        if (zds->fParams.windowSize > zds->maxWindowSize)
                                return ERROR(frameParameter_windowTooLarge);

                        /* Buffers are preallocated, but double check */
                        {
                                size_t const blockSize = MIN(zds->maxWindowSize, ZSTD_BLOCKSIZE_ABSOLUTEMAX);
                                size_t const neededOutSize = zds->maxWindowSize + blockSize + WILDCOPY_OVERLENGTH * 2;
                                if (zds->inBuffSize < blockSize) {
                                        return ERROR(GENERIC);
                                }
                                if (zds->outBuffSize < neededOutSize) {
                                        return ERROR(GENERIC);
                                }
                                zds->blockSize = blockSize;
                        }
                        zds->stage = zdss_read;
                }
                /* pass-through */

                case zdss_read: {
                        size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds->dctx);
                        if (neededInSize == 0) { /* end of frame */
                                zds->stage = zdss_init;
                                someMoreWork = 0;
                                break;
                        }
                        if ((size_t)(iend - ip) >= neededInSize) { /* decode directly from src */
                                const int isSkipFrame = ZSTD_isSkipFrame(zds->dctx);
                                size_t const decodedSize = ZSTD_decompressContinue(zds->dctx, zds->outBuff + zds->outStart,
                                                                                   (isSkipFrame ? 0 : zds->outBuffSize - zds->outStart), ip, neededInSize);
                                if (ZSTD_isError(decodedSize))
                                        return decodedSize;
                                ip += neededInSize;
                                if (!decodedSize && !isSkipFrame)
                                        break; /* this was just a header */
                                zds->outEnd = zds->outStart + decodedSize;
                                zds->stage = zdss_flush;
                                break;
                        }
                        if (ip == iend) {
                                someMoreWork = 0;
                                break;
                        } /* no more input */
                        zds->stage = zdss_load;
                        /* pass-through */
                }

                case zdss_load: {
                        size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds->dctx);
                        size_t const toLoad = neededInSize - zds->inPos; /* should always be <= remaining space within inBuff */
                        size_t loadedSize;
                        if (toLoad > zds->inBuffSize - zds->inPos)
                                return ERROR(corruption_detected); /* should never happen */
                        loadedSize = ZSTD_limitCopy(zds->inBuff + zds->inPos, toLoad, ip, iend - ip);
                        ip += loadedSize;
                        zds->inPos += loadedSize;
                        if (loadedSize < toLoad) {
                                someMoreWork = 0;
                                break;
                        } /* not enough input, wait for more */

                        /* decode loaded input */
                        {
                                const int isSkipFrame = ZSTD_isSkipFrame(zds->dctx);
                                size_t const decodedSize = ZSTD_decompressContinue(zds->dctx, zds->outBuff + zds->outStart, zds->outBuffSize - zds->outStart,
                                                                                   zds->inBuff, neededInSize);
                                if (ZSTD_isError(decodedSize))
                                        return decodedSize;
                                zds->inPos = 0; /* input is consumed */
                                if (!decodedSize && !isSkipFrame) {
                                        zds->stage = zdss_read;
                                        break;
                                } /* this was just a header */
                                zds->outEnd = zds->outStart + decodedSize;
                                zds->stage = zdss_flush;
                                /* pass-through */
                        }
                }

                case zdss_flush: {
                        size_t const toFlushSize = zds->outEnd - zds->outStart;
                        size_t const flushedSize = ZSTD_limitCopy(op, oend - op, zds->outBuff + zds->outStart, toFlushSize);
                        op += flushedSize;
                        zds->outStart += flushedSize;
                        if (flushedSize == toFlushSize) { /* flush completed */
                                zds->stage = zdss_read;
                                if (zds->outStart + zds->blockSize > zds->outBuffSize)
                                        zds->outStart = zds->outEnd = 0;
                                break;
                        }
                        /* cannot complete flush */
                        someMoreWork = 0;
                        break;
                }
                default:
                        return ERROR(GENERIC); /* impossible */
                }
        }

        /* result */
        input->pos += (size_t)(ip - istart);
        output->pos += (size_t)(op - ostart);
        {
                size_t nextSrcSizeHint = ZSTD_nextSrcSizeToDecompress(zds->dctx);
                if (!nextSrcSizeHint) {                     /* frame fully decoded */
                        if (zds->outEnd == zds->outStart) { /* output fully flushed */
                                if (zds->hostageByte) {
                                        if (input->pos >= input->size) {
                                                zds->stage = zdss_read;
                                                return 1;
                                        }            /* can't release hostage (not present) */
                                        input->pos++; /* release hostage */
                                }
                                return 0;
                        }
                        if (!zds->hostageByte) { /* output not fully flushed; keep last byte as hostage; will be released when all output is flushed */
                                input->pos--;    /* note : pos > 0, otherwise, impossible to finish reading last block */
                                zds->hostageByte = 1;
                        }
                        return 1;
                }
                nextSrcSizeHint += ZSTD_blockHeaderSize * (ZSTD_nextInputType(zds->dctx) == ZSTDnit_block); /* preload header of next block */
                if (zds->inPos > nextSrcSizeHint)
                        return ERROR(GENERIC); /* should never happen */
                nextSrcSizeHint -= zds->inPos; /* already loaded*/
                return nextSrcSizeHint;
        }
}

EXPORT_SYMBOL(ZSTD_DCtxWorkspaceBound);
EXPORT_SYMBOL(ZSTD_initDCtx);
EXPORT_SYMBOL(ZSTD_decompressDCtx);
EXPORT_SYMBOL(ZSTD_decompress_usingDict);

EXPORT_SYMBOL(ZSTD_DDictWorkspaceBound);
EXPORT_SYMBOL(ZSTD_initDDict);
EXPORT_SYMBOL(ZSTD_decompress_usingDDict);

EXPORT_SYMBOL(ZSTD_DStreamWorkspaceBound);
EXPORT_SYMBOL(ZSTD_initDStream);
EXPORT_SYMBOL(ZSTD_initDStream_usingDDict);
EXPORT_SYMBOL(ZSTD_resetDStream);
EXPORT_SYMBOL(ZSTD_decompressStream);
EXPORT_SYMBOL(ZSTD_DStreamInSize);
EXPORT_SYMBOL(ZSTD_DStreamOutSize);

EXPORT_SYMBOL(ZSTD_findFrameCompressedSize);
EXPORT_SYMBOL(ZSTD_getFrameContentSize);
EXPORT_SYMBOL(ZSTD_findDecompressedSize);

EXPORT_SYMBOL(ZSTD_isFrame);
EXPORT_SYMBOL(ZSTD_getDictID_fromDict);
EXPORT_SYMBOL(ZSTD_getDictID_fromDDict);
EXPORT_SYMBOL(ZSTD_getDictID_fromFrame);

EXPORT_SYMBOL(ZSTD_getFrameParams);
EXPORT_SYMBOL(ZSTD_decompressBegin);
EXPORT_SYMBOL(ZSTD_decompressBegin_usingDict);
EXPORT_SYMBOL(ZSTD_copyDCtx);
EXPORT_SYMBOL(ZSTD_nextSrcSizeToDecompress);
EXPORT_SYMBOL(ZSTD_decompressContinue);
EXPORT_SYMBOL(ZSTD_nextInputType);

EXPORT_SYMBOL(ZSTD_decompressBlock);
EXPORT_SYMBOL(ZSTD_insertBlock);